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

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

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