Unused string keys

[arouinfar]

For #440

When reviewing the strings in Studio, I realized that there are two unused string keys -- earthDayStringProperty & earthMinuteStringProperty. These are both singular versions of the timeCounter string, however, only the plural version is ever used in the sim.

@samreid can you confirm if these string keys are being used somewhere in the sim? If not, can we get rid of them?

[samreid]

I fixed this code and it should now be using the singular strings.

@arouinfar can you please review?

[arouinfar]

Thanks @samreid. Looks good in master, but not in rc.1, so tagging for cherry-picking.

[samreid]

Needed for phetsims/qa#841

[Nancy-Salpepi]

The singular strings have been added to RC.3. Keeping this issue open because of #463.

[samreid]

We pushed a fix in #463 and @marlitas and I confirmed the strings are correctly omitted. Leaving open for verification in RC after cherry-picking the commits from #463

[samreid]

Please close after verifying.

[KatieWoe]

This seems to be broken again in phetsims/qa#850

[Nancy-Salpepi]

@KatieWoe they decided to always go back to always plural because of #463

[samreid]

From discussion with @KatieWoe

[KatieWoe]

Closing. Looks ok in RC 4