fix(ci): use appimage container: owncloudci/appimage-build:sles15-amd64

Author: DeepDiver1975

.github/workflows/main.yml

@@ -47,7 +47,7 @@ jobs:
             - name: linux-gcc-x86_64
               target: linux-64-gcc
               os: ubuntu-latest
-              container: owncloudci/appimage-build:centos7-devtoolset11-amd64
+              container: owncloudci/appimage-build:sles15-amd64
               fetch-depth: 1
 
     name: ${{ matrix.name }}