[infra] Increase Linux ARM64 sanitizer test coverage.

Change-Id: Id9086913d0c3b7a0d88eaeb2ce8f2be17f80e285
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/510541
Reviewed-by: Alexander Aprelev <aam@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

tools/bots/test_matrix.json

@@ -1578,7 +1578,7 @@
             "-nvm-${sanitizer}-${system}-${mode}-${arch}",
             "ffi",
             "standalone",
-            "vm/dart/tsan"
+            "vm/dart"
           ],
           "fileset": "vm",
           "shards": 2
@@ -1589,7 +1589,7 @@
             "-nvm-aot-${sanitizer}-${system}-${mode}-${arch}",
             "ffi",
             "standalone",
-            "vm/dart/tsan"
+            "vm/dart"
           ],
           "fileset": "vm",
           "shards": 4