[bazel] Fix nanobind header build (#192627)
The build was broken by 3b3ac5a1169722bff1ae0f5f8f27a48cc08c3d02
changing textual_hdrs to hdrs - the copts/features weren't copied over,
meaning Nanobind was attempted to be built with exceptions disabled.
Co-authored-by: James Molloy <jmolloy@google.com>
