[bazel] Extra layering_check dep for #151228: BFloat16 (#152741)

Author: rupprecht

utils/bazel/llvm-project-overlay/libc/utils/MPFRWrapper/BUILD.bazel

@@ -77,6 +77,7 @@ libc_test_library(
         "//libc:__support_cpp_string_view",
         "//libc:__support_cpp_stringstream",
         "//libc:__support_cpp_type_traits",
+        "//libc:__support_fputil_bfloat16",
         "//libc:__support_fputil_cast",
         "//libc:__support_fputil_fp_bits",
         "//libc:__support_fputil_fpbits_str",