Revert "Android: Add BuildConfig.IS_PROGUARD_ENABLED and BuildConfig.IS_CRONET_BUILD"

This reverts commit 9e6d72ca61fd707ec9af7ae41a27d62b6baab268.

Reason for revert: Broke cronet:
https://ci.chromium.org/ui/p/chromium/builders/ci/android-cronet-arm-rel/144975/overview

Original change's description:
> Android: Add BuildConfig.IS_PROGUARD_ENABLED and BuildConfig.IS_CRONET_BUILD
>
> These should be needed rarely, but are useful nonetheless.
>
> Bug: None
> Change-Id: If421164600fef1e2675feee6c7d86cb8c0580c02
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5537749
> Auto-Submit: Andrew Grieve <agrieve@chromium.org>
> Commit-Queue: Andrew Grieve <agrieve@chromium.org>
> Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
> Owners-Override: Andrew Grieve <agrieve@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1300687}

Bug: None
Change-Id: I1c2e83334b59386507677a4b1403457f9073d94a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5539389
Owners-Override: Andrew Grieve <agrieve@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1300752}