Xcodeproj: remove explicit CLANG_CXX_LANGUAGE_STANDARD setting

This fixes warnings generated by pod install and it's also not needed to define them ourself

VLC.xcodeproj/project.pbxproj

@@ -3648,7 +3648,6 @@
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
-				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_ENABLE_OBJC_WEAK = YES;
@@ -3687,7 +3686,6 @@
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
-				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_ENABLE_OBJC_WEAK = YES;
@@ -3726,7 +3724,6 @@
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
-				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_ENABLE_OBJC_WEAK = YES;
@@ -4040,7 +4037,6 @@
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				CLANG_ANALYZER_LOCALIZABILITY_NONLOCALIZED = YES;
-				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
@@ -4096,7 +4092,6 @@
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				CLANG_ANALYZER_LOCALIZABILITY_NONLOCALIZED = YES;
-				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
@@ -4230,7 +4225,6 @@
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				CLANG_ANALYZER_LOCALIZABILITY_NONLOCALIZED = YES;
-				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;