ci: make rvm version comments consistent

.gitlab/ci/docker/debian10/install_rvm.sh

@@ -14,6 +14,7 @@ gpg2 --keyserver hkps://keyserver.ubuntu.com \
 
 curl -sSL https://get.rvm.io | bash -s stable
 
+# keep version in sync with `env_debian*_ninja.sh`
 /usr/local/rvm/bin/rvm install ruby-2.7.0
 
 tar -C /usr/local -cf /root/rvm.tar rvm

.gitlab/ci/docker/fedora35/install_rvm.sh

@@ -13,9 +13,7 @@ dnf install --setopt=install_weak_deps=False -y \
 
 curl -sSL https://get.rvm.io | bash -s stable
 
-# This is intentionally an older version.
-# If updating, the associated `env_fedora*_makefiles.cmake` file needs updated
-# as well.
+# keep version in sync with `env_fedora*_makefiles.cmake`
 /usr/local/rvm/bin/rvm install ruby-2.7.0
 
 tar -C /usr/local -cf /root/rvm.tar rvm