android: Fix links to android_emulator.md

The other pages were referring to android_emulators.md (plural), which does
not exist.

TBR=agrieve

Change-Id: I6bd1c2ac95f851b8aae02550c650607ed2182a1f
Reviewed-on: https://chromium-review.googlesource.com/1103569
Reviewed-by: Raphael Kubo da Costa <[email protected]>
Commit-Queue: Raphael Kubo da Costa <[email protected]>
Cr-Commit-Position: refs/heads/master@{#568763}
diff --git a/docs/android_test_instructions.md b/docs/android_test_instructions.md
index 9e10a69..6fc4649 100644
--- a/docs/android_test_instructions.md
+++ b/docs/android_test_instructions.md
@@ -54,7 +54,7 @@
 ### Using Emulators
 
 Running tests on emulators is the same as on device. Refer to
-[android_emulators.md](android_emulators.md) for setting up emulators.
+[android_emulator.md](android_emulator.md) for setting up emulators.
 
 ## Building Tests