test: Fix act errors in ExploreChartPanel test

[lyndsiWilliams]

SUMMARY

This PR fixes 3 act errors in superset-frontend/src/explore/components/ExploreChartPanel.test.jsx

TESTING INSTRUCTIONS

• cd into superset-frontend/src/explore/components
• run npm run test superset-frontend/src/explore/components/ExploreChartPanel.test.jsx
• Observe that there are no act errors in the console

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• 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 #21456 (6f2323f) into master (05b97ff) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #21456      +/-   ##
==========================================
+ Coverage   66.56%   66.59%   +0.02%     
==========================================
  Files        1791     1791              
  Lines       68608    68676      +68     
  Branches     7320     7355      +35     
==========================================
+ Hits        45671    45733      +62     
- Misses      21044    21047       +3     
- Partials     1893     1896       +3     

Flag	Coverage Δ
hive	52.93% <ø> (ø)
javascript	52.82% <ø> (+0.07%)	⬆️
mysql	78.08% <ø> (ø)
postgres	78.14% <ø> (ø)
presto	52.83% <ø> (ø)
python	81.30% <ø> (ø)
sqlite	76.64% <ø> (ø)
unit	50.96% <ø> (ø)

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

Impacted Files	Coverage Δ
.../plugin-chart-echarts/src/Timeseries/buildQuery.ts	60.00% <0.00%> (-6.67%)	⬇️
.../CRUD/data/database/DatabaseModal/ExtraOptions.tsx	80.00% <0.00%> (-3.34%)	⬇️
...et-ui-chart-controls/src/operators/sortOperator.ts	100.00% <0.00%> (ø)
...frontend/src/components/DatabaseSelector/index.tsx	96.03% <0.00%> (+0.80%)	⬆️
...et-frontend/src/components/TableSelector/index.tsx	78.57% <0.00%> (+2.57%)	⬆️

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