Revert "[bazel] Add missing `includes` path."

This reverts commit e8d9a6e8573fe0eb952474c76045b2d8d28bfa17.

Reason for revert: Duplicate `includes` definition with the same value.

Original change's description:
> [bazel] Add missing `includes` path.
>
> Add `includes = ["."]` to the `BUILD.bazel` file. This is
> necessary to allow dependents to compile with a simple
> `#include <zlib.h>` line, like libcurl (and others) do.
>
> Testing: fx build --host @//third_party/curl:libcurl
> Change-Id: I6bb48338b34d4f31e5e08fe2b18478605885eaaf
> Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/zlib/+/1779074
> Reviewed-by: Francois Rousseau <frousseau@google.com>

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I4232c1b43615a16b4fd6017b24fd37e41c637a02
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/zlib/+/1774557
Exempt: android-build-ayeaye@system.gserviceaccount.com <android-build-ayeaye@system.gserviceaccount.com>