Revert "Fix shallow clones when upstream attribute is present"

This reverts commit d9cc0a1526.

Reason for revert: AttributeError: 'Project' object has no attribute 'use_superproject'

Bug: b/427093249
Change-Id: I57b285ab21f58b040e68ec14b85425f43f0abcca
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/498641
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Gavin Mak <gavinmak@google.com>

project.py

@@ -2411,9 +2411,7 @@ class Project:
             # throws an error.
             revs = [f"{self.revisionExpr}^0"]
             upstream_rev = None
-
+            if self.upstream:
-            # Only check upstream when using superproject.
-            if self.upstream and self.use_superproject:
                 upstream_rev = self.GetRemote().ToLocal(self.upstream)
                 revs.append(upstream_rev)
 
@@ -2425,9 +2423,7 @@ class Project:
                 log_as_error=False,
             )
 
-            # Only verify upstream relationship for superproject scenarios
+            if self.upstream:
-            # without affecting plain usage.
-            if self.upstream and self.use_superproject:
                 self.bare_git.merge_base(
                     "--is-ancestor",
                     self.revisionExpr,