Improve Turkish translations

[bitigchi]

Updates the strings to be more in-line with the Apple terminology, and capitalisation. Ambiguities have been found and fixed as well.

(Insert summary of your pull request here)

Fixes # (issue)

Misc Checklist

• My change requires a documentation update on Sparkle's website repository
• My change requires changes to generate_appcast, generate_keys, or sign_update

Testing

I tested and verified my change by using one or multiple of these methods:

• Sparkle Test App
• Unit Tests
• My own app
• Other (please specify)

(Describe all the cases that were tested)

macOS version tested: [place version here]

[zorgiepoo]

Thanks!