Remove libsurfaceflinger_unittest from root TEST_MAPPING

libsurfaceflinger_unittest has some flaky tests, and being run for all
frameworks/native changes means submitters are having to rerun
presubmit.

Bug: 186417847
Test: None (presubmit only)
Change-Id: Ie1f9542f8304493cdc40aec00e374a88cef42853
Merged-In: I99f9fdf5e75dae686f958e97e9685d1a00166877
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 8173c89..f7d1dde 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -55,9 +55,6 @@
           "include-filter": "*RelativeZTest.*"
         }
       ]
-    },
-    {
-      "name": "libsurfaceflinger_unittest"
     }
   ]
 }