net-im/tg_owt: Fix installed include to work with clang13

Import code from upstream fixing an issue in an installed include
file causing telegram-desktop [1] to fail to build on recent head after
the import of clang13.

PR: 260042, 260040 [1]
Approved by: build fix blanket
Obtained from: https://github.com/abseil/abseil-cpp/commit/e19260fd7dbef881492fd73891e0be5bd4a09b95