Fixing bug with RedTeamingBot attack strategy

[rlundeen2]

Description

Previously in RedTeamingBot, attack_strategy was mandatory but documented as okay to be empty. This is problematic because then the is_chat_complete function doesn't always detect the end of a conversation since the token isn't present. A couple of our notebooks were broken because of this. This PR does the following:

• Sets attack_strategy by default to a valid value
• In init, check that the complete token is present in the attack_strategy

Tests

• no new tests required
• new tests added
• existing tests adjusted

Documentation

• no documentation changes needed
• documentation added or edited
• example notebook added or updated

[github-actions]

Test Results

85 tests  +2   85 ✅ +2   8s ⏱️ +2s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit acd591e. ± Comparison against base commit c070249.

♻️ This comment has been updated with latest results.