fix(examples): calendar chart metric should be metrics

[villebro]

SUMMARY

One of the example calendar heatmap charts has incorrectly defined the metric control value, while it really should be metrics (the value should also be an array of strings, not a string).

BEFORE

AFTER

TESTING INSTRUCTIONS

1. Populate examples data
2. Open the "Calendar Heatmap" chart
3. See that previously it didn't work, but after the changes it works properly.

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #15173 (a88d592) into master (7237324) will decrease coverage by 0.07%.
The diff coverage is n/a.

❗ Current head a88d592 differs from pull request most recent head e0367fe. Consider uploading reports for the commit e0367fe to get more accurate results

@@            Coverage Diff             @@
##           master   #15173      +/-   ##
==========================================
- Coverage   77.16%   77.09%   -0.08%     
==========================================
  Files         971      971              
  Lines       50243    50243              
  Branches     6112     6112              
==========================================
- Hits        38772    38736      -36     
- Misses      11268    11304      +36     
  Partials      203      203              

Flag	Coverage Δ
hive	?
mysql	81.70% <ø> (+<0.01%)	⬆️
postgres	81.71% <ø> (ø)
presto	81.42% <ø> (?)
python	81.95% <ø> (-0.14%)	⬇️
sqlite	?

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

Impacted Files	Coverage Δ
superset/examples/random_time_series.py	20.58% <ø> (ø)
superset/db_engines/hive.py	0.00% <0.00%> (-82.15%)	⬇️
superset/db_engine_specs/hive.py	69.20% <0.00%> (-17.21%)	⬇️
superset/db_engine_specs/sqlite.py	91.89% <0.00%> (-5.41%)	⬇️
superset/utils/celery.py	86.20% <0.00%> (-3.45%)	⬇️
superset/result_set.py	96.77% <0.00%> (-1.62%)	⬇️
superset/utils/cache.py	73.26% <0.00%> (-1.00%)	⬇️
superset/utils/core.py	88.93% <0.00%> (-0.13%)	⬇️
superset/models/core.py	90.02% <0.00%> (+0.26%)	⬆️
superset/connectors/sqla/models.py	89.33% <0.00%> (+0.94%)	⬆️
... and 1 more

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[rusackas]

/testenv up

[github-actions]

@rusackas Ephemeral environment spinning up at http://54.212.78.129:8080. Credentials are admin/admin. Please allow several minutes for bootstrapping and startup.

[rusackas]

Not sure why the presto/hive CI action keeps failing, but the code LGTM and it sure seems to have fixed the problem in manual testing!

[rusackas]

I've restarted the presto/hive tests a third time now. If it doesn't pass, it doesn't seem like flakiness. The error doesn't look like it has anything to do with this PR though.

[rusackas]

You might need to rebase this to bring in #15163 to fix the Presto/Hive tests

[github-actions]

Ephemeral environment shutdown and build artifacts deleted.