Reverts "Uninstall microbenchmarks before running them. (#154183)" (#154200)

Reverts: flutter/flutter#154183
Initiated by: zanderso
Reason for reverting: microbenchmarks timing out on CI.
Original PR Author: jtmcdole

Reviewed By: {andrewkolos}

This change reverts the following previous change:
Flakes in #153828 stem from adb saying the app isn't installed, but then failing to install wtih `-r`. Several other tests uninstall the app before trying to run it.

Potential corrects #153828

dev/devicelab/lib/tasks/microbenchmarks.dart

@@ -30,18 +30,6 @@ TaskFunction createMicrobenchmarkTask({
         final Directory appDir = dir(
             path.join(flutterDirectory.path, 'dev/benchmarks/microbenchmarks'));
         final Process flutterProcess = await inDirectory(appDir, () async {
-          section('Uninstall microbenchmarks app ($benchmarkPath)');
-
-          await flutter(
-            'install',
-            options: <String>[
-              '-v',
-              '--uninstall-only',
-              '-d',
-              device.deviceId,
-            ],
-          );
-
           final List<String> options = <String>[
             '-v',
             // --release doesn't work on iOS due to code signing issues