[clang-tidy] Fix FP in cppcoreguidelines-missing-std-forward in lambda init-list (#190522)
In `TK_IgnoreUnlessSpelledInSource` mode
[`MatchChildASTVisitor::TraverseLambdaExpr`](https://github.com/llvm/llvm-project/blob/main/clang/lib/ASTMatchers/ASTMatchFinder.cpp#L280)
only calls `match()` on each capture-init expression without recursing
into its children. So for `[t{std::forward<T>(t)}]` the `CallExpr`
nested inside the `InitListExpr` is never visited, and
`ForwardCallMatcher` never binds "call".
Fixes https://github.com/llvm/llvm-project/issues/150446.