message: Update FIPS documentation with correct flag path.
diff: @@ -68,7 +68,7 @@ WORKSPACE](https://github.com/google/tink/blob/master/cc/WORKSPACE).
  To build Tink in FIPS-only mode, you simply set a flag at compile time:
  ```shell
  -bazel build ... --//third_party/tink/cc/config:use_only_fips=True
  +bazel build ... --//config:use_only_fips=True
  ```
  If you want to check at runtime whether Tink has been build in FIPS only mode,
  