Remove unnecessary code from release script (#10426)

This code [never did
anything](https://github.com/certbot/certbot/pull/10417#issuecomment-3190266418),
and it is not now. Let's remove it so we don't have to keep taking it
into account. I did a test release and it removed the `dev0`s just fine.

tools/_release.sh

@@ -101,12 +101,6 @@ git checkout "$RELEASE_BRANCH"
 towncrier build --version "$version" --yes
 git commit -m "Update changelog for $version release"
 
-for pkg_dir in $SUBPKGS certbot-compatibility-test
-do
-  sed -i 's/\.dev0//' "$pkg_dir/setup.py"
-  git add "$pkg_dir/setup.py"
-done
-
 SetVersion() {
     ver="$1"
     # bumping Certbot's version number is done differently