Bump the default clang version to 13.0.0

Author: shahmishal

utils/build_swift/build_swift/defaults.py

@@ -50,7 +50,7 @@
 
 COMPILER_VENDOR = 'none'
 SWIFT_USER_VISIBLE_VERSION = Version('5.6')
-CLANG_USER_VISIBLE_VERSION = Version('10.0.0')
+CLANG_USER_VISIBLE_VERSION = Version('13.0.0')
 SWIFT_ANALYZE_CODE_COVERAGE = 'false'
 
 DARWIN_XCRUN_TOOLCHAIN = 'default'