chore: Rename pull-build-template-operator to build-template-operator (…

…#248)

**Description**

Changes proposed in this pull request:
- Renaming `pull-build-template-operator` to `build-template-operator`

**Related Issues**
In cooperation with
kyma-project/lifecycle-manager#1811

.github/workflows/pull-build-template-operator.yml → .github/workflows/build-template-operator.yml

@@ -1,4 +1,4 @@
-name: pull-build-template-operator
+name: build-template-operator
 
 on:
   push: