gitannex: speed up the end to end tests by removing redundant checks

The migration test ran the full "git annex testremote" suite for every
layout mode after verifying the migration with "git annex fsck".

The fsck calls already prove the migrated data is accessible via the
builtin special remote, and TestEndToEnd covers the special remote
protocol with testremote, so the extra five full testremote runs
duplicated coverage at a cost of tens of seconds each on CI.

cmd/gitannex/e2e_test.go

@@ -252,8 +252,9 @@ func TestEndToEnd(t *testing.T) {
 	}
 }
 
-// For each layout mode, migrate a single remote from git-annex-remote-rclone to
-// git-annex-remote-rclone-builtin and run `git annex testremote`.
+// For each layout mode, migrate a single remote from git-annex-remote-rclone
+// to git-annex-remote-rclone-builtin and verify that annexed files remain
+// accessible.
 func TestEndToEndMigration(t *testing.T) {
 	skipE2eTestIfNecessary(t)
 
@@ -303,8 +304,6 @@ func TestEndToEndMigration(t *testing.T) {
 			)
 
 			tc.runInRepo(t, "git", "annex", "fsck", "--from=MigratedRemote", "foo")
-
-			tc.runInRepo(t, "git", "annex", "testremote", "MigratedRemote")
 		})
 	}
 }