Fix #2504: Address nit for HomeActivityTest to use verifyHomeRecyclerViewHasGridColumnCount() helper

[yurilev]

Explanation

Fixes #2504: Address nit from pull request #2246 to consistently use the verifyHomeRecyclerViewHasGridColumnCount() helper in HomeActivityTest. There was a sole remaining location where it wasn't used.

Note: The nit was for testHomeActivity_allTopicsCompleted_displaysAllTopicCards(). This method fails when running using Espresso in an Android emulator with a tablet image, because of the bigger screen size. Will file a separate issue to address that. (All tests pass in Robolectric.) Other similar test methods covering "topics":

• Have 4 versions, split into portrait/landscape and mobile/tablet.
• Also assert the number of cards.

Also fixed an adjacent single letter typo.

Checklist

• The PR title starts with "Fix #bugnum: ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• The PR explanation includes the words "Fixes #bugnum: ..." (or "Fixes part of #bugnum" if the PR only partially fixes an issue).
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[yurilev]

Robolectric (app module) fails for a single unrelated test. Did not find preexisting issue covering this, filed #2588.

[yurilev]

@rt4914 PTAL:

• I don't think have the the credentials to assign the PR to you.
• See comment about failing test. Is it a blocker? (re-run both Espresso and Robolectric and the test passes locally)

[yurilev]

Syncing and re-triggering - Robolectric passed in a different pull request. Trying again.

[rt4914]

LGTM, thanks.