add maptask cache clarification

[dansola]

Why are the changes needed?

Confusion regarding map task caching and regular task caching.

What changes were proposed in this pull request?

Docs change

How was this patch tested?

No tests for docs

Check all the applicable boxes

• [x] I updated the documentation accordingly.
• [ ] All new and existing tests passed.
• [x] All commits are signed-off.

Docs link

[codecov[bot]]

Codecov Report

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

Project coverage is 61.09%. Comparing base (43c0f1a) to head (7b4c464). Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5340      +/-   ##
==========================================
- Coverage   61.10%   61.09%   -0.01%     
==========================================
  Files         794      794              
  Lines       51213    51213              
==========================================
- Hits        31292    31288       -4     
- Misses      17039    17044       +5     
+ Partials     2882     2881       -1     

Flag	Coverage Δ
unittests-datacatalog	69.31% <ø> (ø)
unittests-flyteadmin	58.86% <ø> (-0.05%)	:arrow_down:
unittests-flytecopilot	17.79% <ø> (ø)
unittests-flytectl	68.30% <ø> (ø)
unittests-flyteidl	79.30% <ø> (ø)
unittests-flyteplugins	61.94% <ø> (ø)
unittests-flytepropeller	57.32% <ø> (ø)
unittests-flytestdlib	65.73% <ø> (+0.05%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.