ci: fix ci trigger and gitlab image (#4)

Author: lterrac

.github/workflows/master.yml

@@ -4,7 +4,7 @@ name: Merge into master - Build and Run Tests
 
 on:
   push:
-    branches: ["master"]
+    branches: ["main"]
 
 env:
   REGISTRY: ghcr.io

.github/workflows/pr-development.yml

@@ -4,7 +4,7 @@ name: PR development - Build and Run Tests
 
 on:
   pull_request:
-    branches: ["master"]
+    branches: ["main"]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}

.github/workflows/taskr.yml

@@ -1,5 +1,5 @@
 build:
-  image: ghcr.io/algebraic-programming/taskr/buildenv-x86_64:latest
+  image: ghcr.io/algebraic-programming/taskr/buildenv:latest
   variables:
     GIT_SUBMODULE_STRATEGY: recursive
   tags: