chore: support trailing slashes in database api

[diegomedina248]

SUMMARY

Update the database api endpoints so that all custom routes have trailing slashes

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

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TESTING INSTRUCTIONS

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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 #21123 (a955294) into master (fa0be30) will not change coverage.
The diff coverage is 100.00%.

❗ Current head a955294 differs from pull request most recent head d7149cf. Consider uploading reports for the commit d7149cf to get more accurate results

@@           Coverage Diff           @@
##           master   #21123   +/-   ##
=======================================
  Coverage   66.30%   66.30%           
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  Files        1772     1772           
  Lines       67613    67613           
  Branches     7205     7205           
=======================================
  Hits        44832    44832           
  Misses      20938    20938           
  Partials     1843     1843           

Flag	Coverage Δ
javascript	52.08% <ø> (ø)

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Impacted Files	Coverage Δ
superset-frontend/src/SqlLab/actions/sqlLab.js	60.11% <ø> (ø)
superset-frontend/src/views/CRUD/hooks.ts	46.56% <ø> (ø)
superset/databases/api.py	95.49% <100.00%> (ø)

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[zhaoyongjie]

LGTM, It's a safe change, if a user sends a request without trailing then the redirection will be the response.