Revert " add snapcraft package image (master) (#9584)"

This reverts commit ceaedbb.

Author: General-Beck

.gitlab-ci.yml

@@ -226,7 +226,6 @@ build-windows-msvc-x86_64:
 package-linux-snap-amd64:          &package_snap
   stage:                           package
   only:                            *releaseable_branches
-  image:                           parity/snapcraft:gitlab-ci
   cache: {}
   before_script:                   *determine_version
   variables:
@@ -268,7 +267,7 @@ package-linux-snap-armhf:
 publish-linux-snap-amd64:          &publish_snap
   stage:                           publish
   only:                            *publishable_branches
-  image:                           parity/snapcraft:gitlab-ci
+  image:                           snapcore/snapcraft:stable
   cache: {}
   before_script:                   *determine_version
   variables: