Rename ModApiEnvMod and ModApiItemMod

The 'mod' could have meant module in the past but no other classes do this.

src/script/lua_api/l_env.h

@@ -54,7 +54,7 @@ class ModApiEnvBase : public ModApiBase {
 
 };
 
-class ModApiEnvMod : public ModApiEnvBase {
+class ModApiEnv : public ModApiEnvBase {
 private:
 	// set_node(pos, node)
 	// pos = {x=num, y=num, z=num}