Update issue template for bumping GMT versions (#4019)

Author: seisman

.github/ISSUE_TEMPLATE/5-bump_gmt_checklist.md

@@ -27,7 +27,6 @@ using the following command:
   - [ ] Update `.github/workflows/ci_tests.yaml`
   - [ ] Add the legacy GMT version to `.github/workflows/ci_tests_legacy.yaml`
   - [ ] Update GMT 6.x minor version for `extlinks` urls in `doc/conf.py`
-  - [ ] Update GMT 6.x minor version in `.github/workflows/check-links.yml`
 - [ ] Fix failing tests (1 or more PRs)
 - [ ] Fix failing doctests reported in the ["Doctest" workflow](https://github.com/GenericMappingTools/pygmt/actions/workflows/ci_doctests.yaml)
 - [ ] Fix [xfail](https://docs.pytest.org/en/stable/skipping.html#xfail-mark-test-functions-as-expected-to-fail) pytest markers on tests that are now xpass
@@ -36,8 +35,7 @@ using the following command:
 
 - [ ] Bump the minimum required GMT version (1 PR)
   - [ ] Update `required_gmt_version` in `pygmt/clib/__init__.py`
-  - [ ] Update `test_get_default` in `pygmt/tests/test_clib.py`
-  - [ ] Update minimum required versions in `doc/minversions.md`
   - [ ] Remove unsupported GMT version from `.github/workflows/ci_tests_legacy.yaml`
+  - [ ] Ensure minimum required version is correct in `doc/minversions.md`
 - [ ] Remove [xfail](https://docs.pytest.org/en/stable/skipping.html#xfail-mark-test-functions-as-expected-to-fail) pytest markers on tests that are now xpass
 - [ ] Update deprecated syntax in source code and examples based on the [GMT Changelog](https://docs.generic-mapping-tools.org/latest/changes.html)