fix: redundant word in banner for Legacy stream documents

[richsalz]

This does all the changes suggested by @rjsparks in #6902 and a little bit more cleanup

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.77%. Comparing base (c7f6bde) to head (0e72c7e). Report is 20 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7207      +/-   ##
==========================================
- Coverage   88.78%   88.77%   -0.02%     
==========================================
  Files         296      296              
  Lines       41320    41338      +18     
==========================================
+ Hits        36687    36698      +11     
- Misses       4633     4640       +7     

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[rjsparks]

I built and pushed a migration - I suspect Rich missed that and didn't merge back into his branch. Rich - can you cherry pick it from the history, or do you want me to do that and push that commit back in here again?

[richsalz]

@rjsparks if you push the commit, then I'll probably leave this untouched as @jennifer-richards basically approved and I'll just keep my hands off :)

[rjsparks]

for other PRs - if someone else commits to richsalz/datatracker <PR branch>, remember to pull those before rebasing. Also consider never rebasing unless something has gone horribly wrong - rather, just merge main into your work.

[rjsparks]

migration cherry-picked back into the PR

[richsalz]

consider never rebasing

sorry for that. Old habit I picked up with OpenSSL, the first place I learned git.