Update error messages

[ghost]

Description

This updates two error messages defined in app-store.ts.

Message 1 (line 5273)

• Fail goes with to and the infinitive rather than with the gerund. Here’s an example from the Cambridge Dictionary: “John failed to turn up for football practice yesterday” (emphasis added).
• Repository directory needs an article.
• The construction “a common reason . . . is if” is unsuitable here. The conjuction if attaches to is, the sentence suggesting that an undescribed reason occurs under a certain condition. “A common reason . . . is that” will fulfill the function needed.
• I believe the second sentence should be referring to the repository directory or a part of it, not any file or directory at all.

Message 2 (lines 5758–5760)

See the third point above. I’ve also replaced cause with reason for consistency.

Release notes

Notes: no-notes

[tidy-dev]

✨ Thank you for the much better verbiage!

[ghost]

Happy to help!