Don't build dev images on git tags, tag im with latest-itb and sha256

The previous action had a side effect such that whenever someone created a new
tag for some release/release candidate, a new container with latest-itb would
get pushed to Harbor, but from the `dev.Dockerfile` as it exists for that tag.

This essentially means _some_ but not all latest-itb tags weren't actually
tracking main, but other branches instead.

After a chat with Sarthak & Emma, we don't see much use in building dev
containers that aren't produced from the main branch, since we don't do dev
work like that on our release series branches.

This commit removes tags as a trigger from the workflow, and only uses
the image's sha256 and latest-itb as tags

.github/workflows/build-dev-container.yml

@@ -3,10 +3,6 @@ name: Build and Push Dev Image
 on:
   pull_request:
   push:
-    tags:
-      # only build and publish container on v7.0.0 and up
-      - v[7-9]\.[0-9]+\.[0-9]+-**
-      - v[1-9][0-9]+\.[0-9]+\.[0-9]+-**
     branches:
       - main
 
@@ -24,9 +20,7 @@ jobs:
         with:
           images: hub.opensciencegrid.org/pelican_platform/pelican-dev
           tags: |
-            type=semver,pattern={{version}}
             type=raw,value=latest-itb
-            type=ref,enable=true,prefix=itb-,suffix=-{{date 'YYYYMMDDHHmmss'}},event=tag
             type=raw,value=sha-{{sha}}
 
       - name: Set up Docker Buildx