Docs: fix spelling error

This fixes a typo.

Test: N/A
Change-Id: I0e0f61a25b0cb89abf33e55086dd68ecb9e8cd8b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1633772
Commit-Queue: Peter Wen <wnwen@chromium.org>
Auto-Submit: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664420}

docs/android_emulator.md

@@ -93,7 +93,7 @@ for more about how this works.
 ```shell
 $ # Start 8 emulators. Press Ctrl-C to stop them all.
 $ ( for i in $(seq 8); do ~/Android/Sdk/emulator/emulator @EMULATOR_ID -read-only & done; wait )
-$ # Start 12 emulators. More than 10 requires disabling audio on some OS's. Reducing cores increases paralellism.
+$ # Start 12 emulators. More than 10 requires disabling audio on some OS's. Reducing cores increases parallelism.
 $ ( for i in $(seq 12); do ~/Android/Sdk/emulator/emulator @EMULATOR_ID -read-only -no-audio -cores 2 & done; wait )
 ```