Git Basics lesson: Clarify command

[Fiattarone]

Backtick on step 3 of 'Modify a file or two' was way too close to the closing paren and was not visible or immediately apparent.

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1. Because:

Closes #XXXXX

• Because I couldn't tell there was even a backtick! I'm using Google Chrome out of the box on a decade old computer and the backtick looked like it was part of the closing paren.

2. This PR:

• Added a space to make backtick more visible.

3. Additional Information:

N/A