Bump Xcode 12.2 to RC (#10060)

Both xtro and intro looks fine locally, no update required.

Make.config

@@ -60,8 +60,8 @@ IOS_PACKAGE_UPDATE_ID=$(shell printf "2%02d%02d%02d%03d" $(IOS_PACKAGE_VERSION_M
 
 # Xcode version should have both a major and a minor version (even if the minor version is 0)
 XCODE_VERSION=12.2
-XCODE_URL=http://xamarin-storage/bot-provisioning/xcodes/Xcode_12.2_beta_3.xip
-XCODE_DEVELOPER_ROOT=/Applications/Xcode_12.2.0-beta3.app/Contents/Developer
+XCODE_URL=http://xamarin-storage/bot-provisioning/xcodes/Xcode_12.2_GM_seed.xip
+XCODE_DEVELOPER_ROOT=/Applications/Xcode_12.2.0-rc.app/Contents/Developer
 XCODE_PRODUCT_BUILD_VERSION:=$(shell /usr/libexec/PlistBuddy -c 'Print :ProductBuildVersion' $(XCODE_DEVELOPER_ROOT)/../version.plist)
 
 # Mono version embedded in XI/XM (NEEDED_MONO_VERSION/BRANCH) are specified in mk/mono.mk