Update type-check baseline after mrepo initialization

The Python package / test (ubuntu, 3.12) check failed because
basedpyright runs with its baseline locked and reported that the baseline error
count went down by one. Unconditional mrepo initialization resolves the
previous reportPossiblyUnboundVariable diagnostic, so remove that stale
baseline entry.

Validation: basedpyright --warnings; git diff --check.

Author: codex

.basedpyright/baseline.json

@@ -491,14 +491,6 @@
                     "lineCount": 1
                 }
             },
-            {
-                "code": "reportPossiblyUnboundVariable",
-                "range": {
-                    "startColumn": 15,
-                    "endColumn": 20,
-                    "lineCount": 1
-                }
-            },
             {
                 "code": "reportArgumentType",
                 "range": {