[Xcode] libwebrtc does not build for arm64 when the SDK supports arm64e

https://bugs.webkit.org/show_bug.cgi?id=248838
rdar://102397752

Reviewed by Alexey Proskuryakov.

Unset VALID_ARCHS = $(ARCHS_STANDARD_64_BIT), which appears to prevent
libwebrtc from compiling at all when the selected SDK supports arm64e,
but ARCHS is overridden to be arm64.

No other WebKit project use this setting.

* Source/ThirdParty/libwebrtc/Configurations/Base.xcconfig:

Canonical link: https://commits.webkit.org/257540@main

Author: emw-apple

Source/ThirdParty/libwebrtc/Configurations/Base.xcconfig

@@ -88,7 +88,6 @@ ENTITLEMENTS_REQUIRED_USE_INTERNAL_SDK_NO = NO;
 ENTITLEMENTS_REQUIRED_USE_INTERNAL_SDK_YES = $(ENTITLEMENTS_REQUIRED);
 
 SUPPORTED_PLATFORMS = iphoneos iphonesimulator macosx;
-VALID_ARCHS = $(ARCHS_STANDARD_64_BIT);
 
 TARGET_MACOS_LEGACY_VERSION_IDENTIFIER = $(TARGET_MACOS_LEGACY_VERSION_IDENTIFIER_$(MACOSX_DEPLOYMENT_TARGET:base))
 TARGET_MACOS_LEGACY_VERSION_IDENTIFIER_10 = 10$(MACOSX_DEPLOYMENT_TARGET:suffix:identifier)