TEMP - .pytool/CISettings.py: Use Mu Basecore Standalone MM Perf Branch

Temporarily use this branch for testing.

This commit will be reverted after the following Mu Basecore PR is
merged:

microsoft/mu_basecore#1268

Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>

.pytool/CISettings.py

@@ -189,7 +189,7 @@ def GetDependencies(self):
             {
                 "Path": "MU_BASECORE",
                 "Url": "https://github.com/microsoft/mu_basecore.git",
-                "Branch": "dev/202405"
+                "Branch": "feature/add_standalonemm_perf_lib"
             },
             {
                 "Path": "Common/MU_PLUS",