Use apt master component for LEAP packages

Currently, the platform configures the `snapshots` component in
/etc/apt/sources.list.d/leap.list.
`snapshots` contains packages uploaded by feature branches and merge
requests so we change to `master` (which contains packges built from
changes to the master branches.

Resolves: #8828

provider_base/common.json

@@ -77,7 +77,7 @@
     "platform": {
       "apt": {
         "basic": "http://deb.leap.se/platform",
-        "component": "snapshots"
+        "component": "master"
       }
     },
     "soledad": {