fix: remove ref-names from .git_archival.txt (#241)

Removing ref-names is now suggested by setuptools-scm, per
https://setuptools-scm.readthedocs.io/en/latest/usage/#git-archives, as
it may lead to the git archive checksum changing.

Generated by the task: njzjz-bot/njzjz-bot#6.

.git_archival.txt

@@ -1,4 +1,3 @@
 node: $Format:%H$
 node-date: $Format:%cI$
 describe-name: $Format:%(describe:tags=true,match=*[0-9]*)$
-ref-names: $Format:%D$