Bump pglast from 5.0 to 5.8

Bumps [pglast](https://github.com/lelit/pglast) from 5.0 to 5.8.
- [Changelog](https://github.com/lelit/pglast/blob/v5/CHANGES.rst)
- [Commits](lelit/pglast@v5.0...v5.8)

---
updated-dependencies:
- dependency-name: pglast
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -1 +1 @@
-pglast==5.0
+pglast==5.8