Revert "[ios] Allow use of chrome_browser_provider_forward.h from provider"

This reverts commit 53513b6a.

Reason for revert: Use the wrong path.

Original change's description:
> [ios] Allow use of chrome_browser_provider_forward.h from provider
> 
> The provider are not permitted to have dependency on //ios/chrome,
> however they were able to forward-declare ChromeBrowserProvider so
> they ended up with indirect dependency.
> 
> To allow moving the class to the global namespace, allow them to
> include the forwarding header since this does not increase the
> amount of "bad" dependency.
> 
> Bug: 1042208, 1043657
> Change-Id: I838167daa14f16ab65983fd3ebf61267f1a9eedd
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2010796
> Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
> Reviewed-by: Mark Cogan <marq@chromium.org>
> Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#733375}

TBR=marq@chromium.org,sdefresne@chromium.org

Change-Id: Iaa7ff98d55ac57fefb448ff0b9ed246cb2495069
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1042208, 1043657
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2010864Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733388}

ios/public/provider/chrome/browser/DEPS

@@ -10,8 +10,4 @@ include_rules = [
   # Do not allow inclusion of forwarding header in the provider code as the
   # provider is not allowed to depends on //ios/chrome.
   "-ios/public/provider/chrome/browser/browser_state/chrome_browser_state.h",
-
-  # To allow moving ChromeBrowserState to the global namespace, permit the
-  # use of chrome_browser_state_forward.h.
-  "+ios/public/provider/chrome/browser/browser_state/chrome_browser_state_forward.h",
 ]