Revert "Don't require a strict revision match in LLDB."

This reverts commit 3cc2831608.

The compiler's revision check has been relaxed since the feature was introduced
and so it's nos better to reduce the number of special code paths for LLDB in
the compiler to facilitate reasoning about it.

rdar://117824367

tools/lldb-moduleimport-test/lldb-moduleimport-test.cpp

@@ -51,8 +51,8 @@ static bool validateModule(
     llvm::SmallVectorImpl<swift::serialization::SearchPath> &searchPaths) {
   info = swift::serialization::validateSerializedAST(
       data, requiresOSSAModules,
-      /*requiredSDK*/ StringRef(), /*requiresRevisionMatch*/ false,
-      &extendedInfo, /* dependencies*/ nullptr, &searchPaths);
+      /*requiredSDK*/ StringRef(), &extendedInfo, /* dependencies*/ nullptr,
+      &searchPaths);
   if (info.status != swift::serialization::Status::Valid) {
     llvm::outs() << "error: validateSerializedAST() failed\n";
     return false;