Documentation

After reviewing the design and implementation of sqlite3’s new autocommit attribute of PR #93823, here is the follow-up review of the documentation, addressing 9 issues with PR #99435:

• Remove an unnecessary lambda in tests
• Clarify that implicit open or roll back happens in the same method call
• Add connect() to the list of implicit-transaction-opening methods
• Recommend commit() and rollback() in legacy manual commit mode
• Clarify PEP-249-compliant vs legacy transaction control
• Improve wording consistency
• Remove two ambiguous ‘underlying’
• Normalize ‘open transaction’
• Normalize ’transaction control’