Revert "Use (processors-1) for test runs (test defaults to processors/2)" (#22628)

* Revert "Custom offset functionality for Popup Menu Button (#22534)"

This reverts commit f44b277f.

* Revert "Updated the ColorScheme dartdoc: a11y (#22618)"

This reverts commit aa6a27e8.

* Revert "Added support for the Khmer (km) language (#22617)"

This reverts commit 3a87b93f.

* Revert "Use 'Future<void>' insted of 'Future<Null>' in SystemChrome (#22583)"

This reverts commit 37c10acb.

* Revert "Choice Chip Fix (#22589)"

This reverts commit 8d76d37f.

* Revert "Throw if trying to set fs.currentDirectory in tests (#22037)"

This reverts commit 2f6155bf.

* Revert "Use (processors-1) for test runs (test defaults to processors/2) (#22085)"

This reverts commit d44f0030.

dev/bots/test.dart

@@ -4,7 +4,6 @@
 
 import 'dart:async';
 import 'dart:io';
-import 'dart:math' as math;
 
 import 'package:path/path.dart' as path;
 
@@ -200,8 +199,6 @@ Future<Null> _pubRunTest(
   bool enableFlutterToolAsserts = false
 }) {
   final List<String> args = <String>['run', 'test', '-rcompact'];
-  final int concurrency = math.max(1, Platform.numberOfProcessors - 1);
-  args.add('-j$concurrency');
   if (!hasColor)
     args.add('--no-color');
   if (testPath != null)