comment: improve the docstring.

Author: aignas

python/private/full_version.bzl

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"A small helper to ensure that we are working with full versions."
+"""A small helper to ensure that we are working with full versions."""
 
 load("//python:versions.bzl", "MINOR_MAPPING")