test: Fix act errors in FixedOrMetricControl test

[lyndsiWilliams]

SUMMARY

This PR fixes 8 act errors in superset-frontend/src/explore/components/controls/FixedOrMetricControl/FixedOrMetricControl.test.tsx

TESTING INSTRUCTIONS

• cd into superset-frontend
• run npm run test superset-frontend/src/explore/components/controls/FixedOrMetricControl/FixedOrMetricControl.test.tsx
• 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 #22334 (c9e85d4) into master (2f23a9c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #22334   +/-   ##
=======================================
  Coverage   66.85%   66.85%           
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  Files        1847     1847           
  Lines       70561    70561           
  Branches     7737     7737           
=======================================
  Hits        47174    47174           
  Misses      21380    21380           
  Partials     2007     2007           

Flag	Coverage Δ
hive	52.53% <ø> (ø)
javascript	53.80% <ø> (ø)
mysql	77.95% <ø> (ø)
postgres	78.02% <ø> (ø)
presto	52.42% <ø> (ø)
python	81.23% <ø> (ø)
sqlite	76.48% <ø> (ø)
unit	50.92% <ø> (ø)

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