Revert "Ensure WebView 64_32 target uses 32-bit abi as default."

This reverts commit 938da203.

Reason for revert: Trialing this configuration again.

Original change's description:
> Ensure WebView 64_32 target uses 32-bit abi as default.
>
> Chrome will run in 64-bit, but WebView will run in
> 32-bit mode by default.
>
> Change-Id: Idc240b62a5c18c9109c02853459c073e4c53d851
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2536784
> Commit-Queue: Ben Mason <benmason@chromium.org>
> Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> Reviewed-by: Richard Coles <torne@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#828936}

TBR=rmcilroy@chromium.org,torne@chromium.org,rmcilroy@google.com,benmason@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I9a0251f06a83159fded60f9e0a53f240d177ec64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593093Reviewed-by: Ben Mason <benmason@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Ben Mason <benmason@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837047}

android_webview/nonembedded/BUILD.gn

@@ -194,6 +194,7 @@ if (android_64bit_target_cpu) {
     input = "java/AndroidManifest.xml"
     output = trichrome_webview_64_32_android_manifest
     variables = trichrome_jinja_variables + _webview_jinja_variables + [
+                  "use32bitAbi=",
                   "trichrome_version=$trichrome_64_32_version_code",
                   "library=libmonochrome_64.so",
                 ]