Rename OCP bullet chart "unused capacity" label

[dlabrecq]

Renamed OCP bullet chart "unused capacity" label as "unused requests"

https://issues.redhat.com/browse/COST-4976

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.69%. Comparing base (7ce4786) to head (f9d848b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #3823    +/-   ##
========================================
  Coverage   65.69%   65.69%            
========================================
  Files         514      514            
  Lines        9974     9974            
  Branches     2193     2352   +159     
========================================
  Hits         6552     6552            
+ Misses       3418     3175   -243     
- Partials        4      247   +243     

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