[clang][test] Add missing test file to cmake (#99907)

Summary:
Seems like this test was never running with cmake, but is running with
bazel and broke at head.

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Differential Revision: https://phabricator.intern.facebook.com/D60251437

Author: keith

clang/unittests/Tooling/CMakeLists.txt

@@ -40,6 +40,7 @@ add_clang_unittest(ToolingTests
   RecursiveASTVisitorTests/CXXMethodDecl.cpp
   RecursiveASTVisitorTests/CXXOperatorCallExprTraverser.cpp
   RecursiveASTVisitorTests/DeclRefExpr.cpp
+  RecursiveASTVisitorTests/DeductionGuide.cpp
   RecursiveASTVisitorTests/ImplicitCtor.cpp
   RecursiveASTVisitorTests/ImplicitCtorInitializer.cpp
   RecursiveASTVisitorTests/InitListExprPostOrder.cpp