don't disable air checking in biome defs when it isn't necessary

doing so greatly slows down plants_lib by forcing the use of the legacy
mapgen code.

bushes/init.lua

@@ -206,7 +206,6 @@ plantslib:register_generate_plant({
     rarity = 101 - 4,  --3,4
     min_elevation = 1, -- above sea level
 	plantlife_limit = -0.9,
-	check_air = false,
   },
   "abstract_bushes.grow_bush"
 )		
@@ -252,7 +251,6 @@ plantslib:register_generate_plant({
     rarity = 101 - 4,  --3,4
     min_elevation = 1, -- above sea level
 	plantlife_limit = -0.9,
-	check_air = false,
   },
   "abstract_bushes.grow_youngtree2"
 )	

dryplants/juncus.lua

@@ -99,7 +99,6 @@ plantslib:register_generate_plant({
 	near_nodes_vertical = 1,
 	near_nodes_count = 1,
     plantlife_limit = -0.9,
-	check_air = false,
   },
   "abstract_dryplants.grow_juncus"
 )
@@ -121,7 +120,6 @@ plantslib:register_generate_plant({
 	near_nodes_vertical = 1,
 	near_nodes_count = 1,
     plantlife_limit = -0.9,
-	check_air = false,
   },
   "abstract_dryplants.grow_juncus"
-)
+)

dryplants/meadowvariation.lua

@@ -21,7 +21,6 @@ plantslib:register_generate_plant({
     rarity = 25,
     min_elevation = 1, -- above sea level
 	plantlife_limit = -0.9,
-	check_air = false,
   },
   "abstract_dryplants.grow_grass_variation"
-)
+)

dryplants/moregrass.lua

@@ -29,7 +29,6 @@ plantslib:register_generate_plant({
     rarity = 101 - TALL_GRASS_RARITY,
     min_elevation = 1, -- above sea level
 	plantlife_limit = -0.9,
-	check_air = false,
   },
   "abstract_dryplants.grow_grass"
-)
+)

ferns/fern.lua

@@ -147,7 +147,6 @@ plantslib:register_generate_plant({ -- near trees (woodlands)
     humidity_min = 0.4,
     temp_max = -0.5, -- 55 <20>C (too hot?)
     temp_min = 0.75, -- -12 <20>C
-	check_air = false,
   },
   "abstract_ferns.grow_fern"
 )
@@ -174,7 +173,6 @@ plantslib:register_generate_plant({ -- near stone (mountains)
     humidity_min = 0.4,
     temp_max = -0.5, -- 55 <20>C (too hot?)
     temp_min = 0.75, -- -12 <20>C
-	check_air = false,
   },
   "abstract_ferns.grow_fern"
 )
@@ -212,7 +210,6 @@ plantslib:register_generate_plant({ -- near ores (potential mining sites)
     humidity_min = 0.4,
     temp_max = -0.5, -- 55 <20>C (too hot?)
     temp_min = 0.75, -- -12 <20>C
-	check_air = false,
   },
   "abstract_ferns.grow_fern"
 )
@@ -243,8 +240,7 @@ plantslib:register_generate_plant({
     humidity_min = 0.4,
     temp_max = -0.5, -- 55 <20>C (too hot?)
     temp_min = 0.75, -- -12 <20>C
-	check_air = false,
   },
   "abstract_ferns.grow_fern"
 )
-end
+end

ferns/gianttreefern.lua

@@ -371,9 +371,8 @@ plantslib:register_generate_plant({
     plantlife_limit = -0.9,
     --humidity_max = 0.39,--1.0,
     --humidity_min = 0.5,
-    --temp_max = -1,-- -1.2,-- -0.5, -- ~ 55 <20>C
-    --temp_min = -0.35,-- -0.07, -- ~ 25 <20>C
-	check_air = false,
+    --temp_max = -1,-- -1.2,-- -0.5, -- ~ 55C
+    --temp_min = -0.35,-- -0.07, -- ~ 25C
   },
   "abstract_ferns.grow_giant_tree_fern"
 )
@@ -401,8 +400,7 @@ plantslib:register_generate_plant({
     humidity_min = 1.0,
     temp_max = -1.0,
     temp_min = 1.0,
-	check_air = false,
   },
   "abstract_ferns.grow_giant_tree_fern"
 )
-end
+end

ferns/treefern.lua

@@ -212,7 +212,6 @@ plantslib:register_generate_plant({
     humidity_min = 0.4,
     temp_max = -0.5,
     temp_min = 0.13,
-	check_air = false,
   },
   "abstract_ferns.grow_tree_fern"
 )
@@ -240,7 +239,6 @@ plantslib:register_generate_plant({
     humidity_min = 1.0,
     temp_max = -1.0,
     temp_min = 1.0,
-	check_air = false,
   },
   "abstract_ferns.grow_tree_fern"
 )

trunks/generating.lua

@@ -354,7 +354,6 @@ plantslib:register_generate_plant({
 	near_nodes_vertical = 1,
 	near_nodes_count = 1,
     plantlife_limit = -0.9,
-    check_air = false,
   },
   "abstract_trunks.place_trunk"
 )

youngtrees/init.lua

@@ -149,7 +149,6 @@ plantslib:register_generate_plant({
     rarity = 101 - 4,  --3,4
     min_elevation = 1, -- above sea level
 	plantlife_limit = -0.9,
-	check_air = false,
   },
   "abstract_youngtrees.grow_youngtree"
 )