ci: fix wrong tag regex for tower (#644)

In #643, I accidentally included a `v` before the version number in the
regex for matching release tags for the `tower` crate, but not for
`tower-whatever` crates. All previous release tags on this repo don't
use a `v`, so adding it was a mistake. This branch removes it.

.github/workflows/release.yml

@@ -3,8 +3,8 @@ name: create github release
 on:
   push:
     tags:
-      - tower-v[0-9]+.*
-      - tower-[a-z]+-v[0-9]+.*
+      - tower-[0-9]+.*
+      - tower-[a-z]+-[0-9]+.*
 
 jobs:
   create-release: