[spm] Remove Grafana from examples

[pavolloffay]

Which problem is this PR solving?

• Grafana server was not necessary for demonstrating SPM behavior or debugging

Description of the changes

• Remove grafana service
• Update readme

How was this change tested?

• Manually (incidentally ran into an odd issue SPM example seems to be missing rate() function for Request Rate chart #6150)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.47%. Comparing base (e80645b) to head (c342f60).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6148       +/-   ##
===========================================
+ Coverage   48.89%   96.47%   +47.57%     
===========================================
  Files         178      354      +176     
  Lines       10761    20107     +9346     
===========================================
+ Hits         5262    19398    +14136     
+ Misses       5058      524     -4534     
+ Partials      441      185      -256     

Flag	Coverage Δ
badger_v1	8.32% <ø> (ø)
badger_v2	1.68% <ø> (ø)
cassandra-4.x-v1	14.40% <ø> (ø)
cassandra-4.x-v2	1.62% <ø> (ø)
cassandra-5.x-v1	14.40% <ø> (ø)
cassandra-5.x-v2	1.62% <ø> (ø)
elasticsearch-6.x-v1	18.53% <ø> (ø)
elasticsearch-7.x-v1	18.61% <ø> (+<0.01%)	⬆️
elasticsearch-8.x-v1	18.78% <ø> (ø)
elasticsearch-8.x-v2	1.68% <ø> (ø)
grpc_v1	9.50% <ø> (ø)
grpc_v2	7.00% <ø> (-0.01%)	⬇️
kafka-v1	8.89% <ø> (ø)
kafka-v2	1.68% <ø> (ø)
memory_v2	1.67% <ø> (-0.02%)	⬇️
opensearch-1.x-v1	18.66% <ø> (+<0.01%)	⬆️
opensearch-2.x-v1	18.65% <ø> (-0.01%)	⬇️
opensearch-2.x-v2	1.68% <ø> (+0.01%)	⬆️
tailsampling-processor	0.47% <ø> (ø)
unittests	95.38% <ø> (?)

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