Fix: [Actions] "is-tag" variable is the 5th element, not 6th

The 6th is "is-stable-tag", but it is currently broken in meaning.
Betas and RCs are considered "stable", but final releases are not.
This is the reason it was working for RC1, but not for the final
release.

.github/workflows/release.yml

@@ -96,7 +96,7 @@ jobs:
         TZ='UTC' date +"%Y-%m-%d %H:%M UTC" > .release_date
         cat .ottdrev | cut -f 1 -d$'\t' > .version
 
-        if [ $(cat .ottdrev | cut -f 6 -d$'\t') = '1' ]; then
+        if [ $(cat .ottdrev | cut -f 5 -d$'\t') = '1' ]; then
           # Assume that all tags are always releases. Why else make a tag?
           IS_TAG="true"