Reduce example Grafana dashboard uid lengths

[danbarr]

The Grafana dashboard uid field has a max length of 40 characters. This PR reduces the length in the example dashboards so users don't have to fix it themselves when following the blog post / tutorial.

Signed-off-by: Dan Barr 6922515+danbarr@users.noreply.github.com

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.39%. Comparing base (6a9563b) to head (19901e0).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2087      +/-   ##
==========================================
+ Coverage   48.30%   48.39%   +0.09%     
==========================================
  Files         238      238              
  Lines       30006    30034      +28     
==========================================
+ Hits        14494    14535      +41     
+ Misses      14407    14398       -9     
+ Partials     1105     1101       -4     

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