remove confusing text from View Test page

[barna-isaac]

• no longer show "You are viewing the rubric for this test"
• no longer show the "Instructions" heading

See: #1457

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 40.59%. Comparing base (9354fb6) to head (7532d03).
Report is 50 commits behind head on redesign-2024.

Additional details and impacted files

@@                Coverage Diff                @@
##           redesign-2024    #1459      +/-   ##
=================================================
- Coverage          40.69%   40.59%   -0.11%     
=================================================
  Files                494      494              
  Lines              22030    22046      +16     
  Branches            7300     7330      +30     
=================================================
- Hits                8966     8949      -17     
- Misses             12439    12472      +33     
  Partials             625      625              

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