[ASTGen/Tests] Add -disable-availability-checking to regex test cases

Regex is not always available for the default OS versions. For example

  error: 'Regex' is only available in watchOS 9.0 or newer

But the current watchOS deployment target for testing is
`-target x86_64-apple-watchos6.0-simulator`

Author: rintaro

test/ASTGen/regex.swift

@@ -1,14 +1,14 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend %s -dump-parse -enable-bare-slash-regex -enable-experimental-feature ParserASTGen > %t/astgen.ast.raw
-// RUN: %target-swift-frontend %s -dump-parse -enable-bare-slash-regex > %t/cpp-parser.ast.raw
+// RUN: %target-swift-frontend %s -dump-parse -enable-bare-slash-regex -disable-availability-checking -enable-experimental-feature ParserASTGen > %t/astgen.ast.raw
+// RUN: %target-swift-frontend %s -dump-parse -enable-bare-slash-regex -disable-availability-checking > %t/cpp-parser.ast.raw
 
 // Filter out any addresses in the dump, since they can differ.
 // RUN: sed -E 's#0x[0-9a-fA-F]+##g' %t/cpp-parser.ast.raw > %t/cpp-parser.ast
 // RUN: sed -E 's#0x[0-9a-fA-F]+##g' %t/astgen.ast.raw > %t/astgen.ast
 
 // RUN: %diff -u %t/astgen.ast %t/cpp-parser.ast
 
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature ParserASTGen -enable-bare-slash-regex
+// RUN: %target-typecheck-verify-swift -enable-experimental-feature ParserASTGen -enable-bare-slash-regex -disable-availability-checking
 
 // REQUIRES: swift_swift_parser