Removed deprecated Bazel clang config references.
Removed deprecated Bazel clang config references.

The clang_linux and clang_mac Bazel configs were removed in
commit I515c114099d659639a808f74e47d489a68b7af62.

Bug: skia:12541
Change-Id: Ib42764686a19a73164efbcf3d72869574f747b8f
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/553590
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Commit-Queue: Chris Mumford <86e3bd41c0fc7139fc638a34b6b342d4b7b77b85@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia