Changed commit name in do_git_release.sh

pygeodyn/release/do_git_release.sh

@@ -6,5 +6,5 @@ VERSION_NB=$(cat VERSION.txt)
 git rm release/RELEASE.md
 git add VERSION.txt
 git add CHANGELOG.md
-git commit -m "Bump to $VERSION_NB"
+git commit -m "Update to $VERSION_NB"
 git tag "$VERSION_NB"