Revert "Disable failing perf tests on Nexus_5."

This reverts commit ec9be0fd.

Reason for revert: Relanding after increasing trace download timeout to 120s

Original change's description:
> Disable failing perf tests on Nexus_5.
> 
> TBR=nednguyen@google.com
> NOTRY=true
> 
> Bug: 902064
> Change-Id: Ic9f91ba4b263fb4ed435ac7a9dc1a096aa452516
> Reviewed-on: https://chromium-review.googlesource.com/c/1318586
> Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
> Reviewed-by: Ned Nguyen <nednguyen@google.com>
> Commit-Queue: Ned Nguyen <nednguyen@google.com>
> Cr-Commit-Position: refs/heads/master@{#605491}

TBR=nednguyen@google.com,crouleau@chromium.org

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

Bug: 902064
Change-Id: I03804b1a557226498df63eb8a7c0dea31e3f227f
Reviewed-on: https://chromium-review.googlesource.com/c/1334335Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607803}

tools/perf/expectations.config

@@ -140,7 +140,6 @@ crbug.com/901510 [ Nexus6_Webview ] memory.long_running_idle_gmail_tbmv2/* [ Ski
 crbug.com/901510 [ Nexus_5 ] memory.long_running_idle_gmail_tbmv2/* [ Skip ]
 crbug.com/901510 [ Nexus5X_Webview ] memory.long_running_idle_gmail_tbmv2/* [ Skip ]
 crbug.com/901510 [ Nexus_5X ] memory.long_running_idle_gmail_tbmv2/* [ Skip ]
-crbug.com/902064 [ Nexus_5 ] memory.long_running_idle_gmail_background_tbmv2/* [ Skip ]
 
 # Benchmark: memory.long_running_idle_gmail_background_tbmv2
 crbug.com/611167 [ Android_Svelte ] memory.long_running_idle_gmail_background_tbmv2/* [ Skip ]
@@ -364,7 +363,6 @@ crbug.com/799080 [ Nexus_5X Android_Webview ] v8.browsing_mobile-future/browse:s
 crbug.com/799080 [ Nexus_5X Android_Webview ] v8.browsing_mobile-future/browse:social:facebook [ Skip ]
 crbug.com/875159 [ Win_10 ] v8.browsing_desktop-future/browse:social:facebook_infinite_scroll [ Skip ]
 crbug.com/901534 [ Nexus6_Webview ] v8.browsing_mobile-future/browse:news:toi [ Skip ]
-crbug.com/902064 [ Nexus_5 ] v8.browsing_mobile-future/browse:news:toi [ Skip ]
 
 # Benchmark: v8.detached_context_age_in_gc
 crbug.com/770982 [ Win ] v8.detached_context_age_in_gc/Docs_(1_open_document_tab) [ Skip ]