Fix push.tags pattern syntax (#275)

In my  change to #265, I was too clever and tried to add a tag pattern to allow arbitrary dotted numeric tag names. Alas, the github pattern syntax does not allow that: https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#filter-pattern-cheat-sheet

Switching to allow x.y and x.y.z format tags only.

Fixes #274
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index ffe2768..9e2daec 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -18,7 +18,8 @@
 on:
   push:
     tags:
-      - "[0-9]+.[0-9.]+"
+      - "[0-9]+.[0-9]+"
+      - "[0-9]+.[0-9]+.[0-9]+"
 
 jobs:
   build: