Revert "Increases link_pool from 3 to 8 for static and minimal_symbols android builder"

This reverts commit bc25fa082ae26f43edfd0eb0af6929ec03acbe41.

Reason for revert: Bot is running out of memory (see bug)

Original change's description:
> Increases link_pool from 3 to 8 for static and minimal_symbols android builder
>
> This is mainly for proguard steps which make build slow due to restricted parallelism on android_n5x_swarming_rel builder.
> Example build traces from slow builds:
> https://chromium-build-stats.appspot.com/ninja_log/2018/01/31/slave954-c4/ninja_log.slave954-c4.chrome-bot.20180131-023634.24049.gz/trace.html from https://ci.chromium.org/buildbot/tryserver.chromium.android/android_n5x_swarming_rel/351638
> https://chromium-build-stats.appspot.com/ninja_log/2018/01/31/slave617-c4/ninja_log.slave617-c4.chrome-bot.20180131-021253.3583.gz/trace.html from https://ci.chromium.org/buildbot/tryserver.chromium.android/android_n5x_swarming_rel/351634
> https://chromium-build-stats.appspot.com/ninja_log/2018/01/31/slave980-c4/ninja_log.slave980-c4.chrome-bot.20180131-021148.4142.gz/trace.html from https://ci.chromium.org/buildbot/tryserver.chromium.android/android_n5x_swarming_rel/351629
>
> I investigate peak memory usage of some large/long time targets with args.gn of android_n5x_swarming_rel.
> |--------------------------------------------------------+-------------|
> | target                                                 | peak memory |
> |--------------------------------------------------------+-------------|
> | chrome_public_apk.proguard.jar                         | 843076 KB   |
> | chrome_public_test_apk__apk.proguard.jar               | 995208 KB   |
> | chrome/android/monochrome_public_apk/classes.dex       | 1178664 KB  |
> | lib.unstripped/lib_unit_tests__library.so              | 3181252 KB  |
> | android_clang_arm/lib.unstripped/libmonochrome.so      | 2718856 KB  |
> | android_clang_arm/lib.unstripped/libwebviewchromium.so | 2362328 KB  |
> |--------------------------------------------------------+-------------|
>
> So 4GB is sufficient.
> I tested the builder by modifing base_export.h to run linker for many targets in https://chromium-review.googlesource.com/c/894928/4
>
> Bug: 804251
> Change-Id: Ic5f985dba29d063a7541553813561f85c9dd3278
> Reviewed-on: https://chromium-review.googlesource.com/894928
> Commit-Queue: Takuto Ikuta <tikuta@google.com>
> Reviewed-by: agrieve <agrieve@chromium.org>
> Reviewed-by: John Budorick <jbudorick@chromium.org>
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#533547}

TBR=dpranke@chromium.org,agrieve@chromium.org,tikuta@google.com,jbudorick@chromium.org
NOTRY=true
# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 804251, 808582
Change-Id: Iceb52c1bb4e506d9d7fa2eebfd8bdd6f67fa2722
Reviewed-on: https://chromium-review.googlesource.com/900063
Commit-Queue: agrieve <agrieve@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#534161}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 1412ae6723a14a741efa10c3d7d162a3d8a134cb

toolchain/concurrent_links.gni

@@ -35,8 +35,6 @@ if (concurrent_links == -1) {
     _args = [ "--mem_per_link_gb=4" ]
   } else if (is_android && !is_component_build && symbol_level == 2) {
     _args = [ "--mem_per_link_gb=25" ]
-  } else if (is_android && !is_component_build && symbol_level == 1) {
-    _args = [ "--mem_per_link_gb=4" ]
   } else if (is_linux && !is_chromeos && symbol_level == 1) {
     _args = [ "--mem_per_link_gb=3" ]
   } else {