macOS: turn code signing off completely on x64

Previously it was using ad-hoc ('sign to run locally') signing, which breaks on macOS 10.14 and older when a .love is put in the Resources subfolder. Ad-hoc is necessary on Apple Silicon but not x64, if real code signing isn't used.

platform/xcode/love.xcodeproj/project.pbxproj

@@ -438,7 +438,7 @@
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = "OS X AppIcon";
 				CODE_SIGN_ENTITLEMENTS = love.entitlements;
-				CODE_SIGN_IDENTITY = "-";
+				CODE_SIGN_IDENTITY = "";
 				COMBINE_HIDPI_IMAGES = YES;
 				ENABLE_HARDENED_RUNTIME = YES;
 				FRAMEWORK_SEARCH_PATHS = (
@@ -471,7 +471,7 @@
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = "OS X AppIcon";
 				CODE_SIGN_ENTITLEMENTS = love.entitlements;
-				CODE_SIGN_IDENTITY = "-";
+				CODE_SIGN_IDENTITY = "";
 				COMBINE_HIDPI_IMAGES = YES;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				ENABLE_HARDENED_RUNTIME = YES;
@@ -893,7 +893,7 @@
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = "OS X AppIcon";
 				CODE_SIGN_ENTITLEMENTS = love.entitlements;
-				CODE_SIGN_IDENTITY = "-";
+				CODE_SIGN_IDENTITY = "";
 				COMBINE_HIDPI_IMAGES = YES;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				ENABLE_HARDENED_RUNTIME = YES;