Fix typos and en_US/en_GB inconsistency in various files (#12902)

src/script/lua_api/l_areastore.h

@@ -54,7 +54,7 @@ public:
 	~LuaAreaStore();
 
 	// AreaStore()
-	// Creates a AreaStore and leaves it on top of stack
+	// Creates an AreaStore and leaves it on top of stack
 	static int create_object(lua_State *L);
 
 	static void Register(lua_State *L);

src/script/lua_api/l_mainmenu.cpp

@@ -884,7 +884,7 @@ int ModApiMainMenu::l_download_file(lua_State *L)
 		}
 	} else {
 		errorstream << "DOWNLOAD denied: " << absolute_destination
-				<< " isn't a allowed path" << std::endl;
+				<< " isn't an allowed path" << std::endl;
 	}
 	lua_pushboolean(L,false);
 	return 1;

src/script/lua_api/l_mainmenu.h

@@ -37,7 +37,7 @@ private:
 	static std::string getTextData(lua_State *L, std::string name);
 
 	/**
-	 * read a integer variable from gamedata table within lua stack
+	 * read an integer variable from gamedata table within lua stack
 	 * @param L stack to read variable from
 	 * @param name name of variable to read
 	 * @return integer value of requested variable

src/script/lua_api/l_mapgen.cpp

@@ -408,7 +408,7 @@ Biome *read_biome_def(lua_State *L, int index, const NodeDefManager *ndef)
 
 	size_t nnames = getstringlistfield(L, index, "node_cave_liquid", &nn);
 	// If no cave liquids defined, set list to "ignore" to trigger old hardcoded
-	// cave liquid behaviour.
+	// cave liquid behavior.
 	if (nnames == 0) {
 		nn.emplace_back("ignore");
 		nnames = 1;

src/script/lua_api/l_object.cpp

@@ -1813,7 +1813,7 @@ int ObjectRef::l_set_sky(lua_State *L)
 
 		sky_params.type = luaL_checkstring(L, 3);
 
-		// Preserve old behaviour of the sun, moon and stars
+		// Preserve old behavior of the sun, moon and stars
 		// when using the old set_sky call.
 		if (sky_params.type == "regular") {
 			sun_params.visible = true;