MNT: (deps): Bump metpy from 1.2.0 to 1.6.3 in /ci

Bumps [metpy](https://github.com/Unidata/MetPy) from 1.2.0 to 1.6.3.
- [Release notes](https://github.com/Unidata/MetPy/releases)
- [Commits](Unidata/MetPy@v1.2.0...v1.6.3)

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

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

ci/doc_requirements.txt

@@ -1,6 +1,6 @@
 cartopy==0.18.0
 matplotlib==3.5.3
-metpy==1.2.0
+metpy==1.6.3
 scipy==1.7.3
 sphinx==5.2.3
 sphinx_rtd_theme==1.0.0