[#57] ci: Disable automatic publishing of unsigned nugets

We're switching to non-automatic process for publishing signed nugets,
unsigned workflow will still be available as an escape hatch but it won't
ever be triggered automatically.

Signed-off-by: Vitaliy Potyarkin <v.potyarkin@yadro.com>

.forgejo/workflows/publish.yml

@@ -1,5 +1,4 @@
 on:
-  push:
   workflow_dispatch:
 
 jobs:
@@ -16,7 +15,7 @@ jobs:
         # `dotnet build` implies and replaces `dotnet pack` thanks to `GeneratePackageOnBuild`
         run: dotnet build
 
-      - name: Publish NuGet packages
+      - name: Publish unsigned NuGet packages
         run: |-
           dotnet nuget add source \
             --name "$NUGET_REGISTRY" \