Revert "Migrate to use pub workspace"

This reverts commit b9b77058a9.


Revert "Add missing sample pubspec to workspace"

This reverts commit 892ea15ac7.


These seem to break the engine.

Change-Id: Ieee26deb7928c3869a1b6265326c3ce568ffe731
Tested: this is a revert.
CoreLibraryReviewExempt: this is a revert
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/415582
Commit-Queue: Sigurd Meldgaard <sigurdm@google.com>
Reviewed-by: Alexander Thomas <athom@google.com>

samples/ffi/http/pubspec.yaml

@@ -2,10 +2,8 @@ name: http_sample
 version: 0.0.1
 publish_to: none
 
-resolution: workspace
-
 environment:
-  sdk: ^3.5.0
+  sdk: '>=3.1.0 <4.0.0'
 
 dependencies:
   ffi: ^2.1.0