fix(config): correct Critters and Companions spawn keys to snake_case

YACL serialises config with FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES
(and serializeNulls), so the camelCase keys biomeSpec, leafInsect, seaBunny,
stagBeetle, rolyPoly and stickBug were never read. Every SpawnEntry then
deserialised with biomeSpec = null, and CAC 2.7.0's SpawnEntry.isTag() calls
biomeSpec.startsWith("#") without a null check, crashing FMLCommonSetup on
both the dedicated server and the client.

Rename the keys; all tuned weights and biome specs are unchanged. Missing
keys still fall back to mod defaults (partial file). Refresh the index and
pack hashes.

pack.toml

@@ -6,7 +6,7 @@ pack-format = "packwiz:1.1.0"
 [index]
 file = "index.toml"
 hash-format = "sha256"
-hash = "3c17e58506c00f8c5aba5151afa765fdd68245c384293a017a5e2062ac35afbe"
+hash = "121d9177b8ca74535005b85160a3e314bc9c95f8c87671b3d6947cb8d52c37e1"
 
 [versions]
 minecraft = "1.21.1"