Use correct type in various get source commands

This fixes a bug where the wrong type was displayed for various
`get source` commands.

```console
$ flux get sources helm --namespace default
✗ no Bucket objects found in default namespace
```

Signed-off-by: Hidde Beydals <hello@hidde.co>

cmd/flux/get_source_git.go

@@ -35,7 +35,7 @@ var getSourceGitCmd = &cobra.Command{
   flux get sources git --all-namespaces
 `,
 	RunE: getCommand{
-		apiType: bucketType,
+		apiType: gitRepositoryType,
 		list:    &gitRepositoryListAdapter{&sourcev1.GitRepositoryList{}},
 	}.run,
 }