[clang-tools-extra] [clang-tidy] Enable `modernize-return-braced-init-list`'s tests in C++11 (PR #158196)

[Victor Chernyakin via cfe-commits]

localspook wrote:

Some statistics: if we decide to force specifying `-std`, we would need to fix ~620 test files (number found by looking for 
`*.{c,cpp,m,mm}` files under `clang-tools-extra/test/clang-tidy` that don't contain the string `-std`). Doable if a bit tedious.

https://github.com/llvm/llvm-project/pull/158196