docs: correct grammar in user-manual/translate.mdx

[araaish]

Summary

• Fixed subject-verb agreement ("inherits", "are currently supported", "that use")
• Fixed incorrect word ("automatically" for "manually", "from happening", "content")
• Fixed verb forms ("translate", "depending on", "suggest translating")
• Fixed article usage ("a specific part", "the translation feature", "on the ... website")
• Fixed duplicate step number (two step 6s → 6 and 7)
• Fixed uncountable noun usage ("text", "content", "languages")

Validation

• Verify rendered page at /user-manual/translate looks correct