fix(plugin-generator): Addresses linter errors in newly generated Superset plugin

[alex-bain]

SUMMARY

When creating a new Superset plugin using the plugin generator, the generated code contains linter errors that prevent Superset from building properly. This PR updates the generator erb templates so that they do not contain linter errors.

Note: Plugins with very long names may still generate linter errors, due to excessive line length

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before:

After:

(Build completes without errors)

TESTING INSTRUCTIONS

• Create a new plugin using the Superset plugin generator in the superset-frontend/plugins/ directory
• Run npm run build from the superset-frontend directory
• Confirm that build completes without linter errors (pre-existing warnings have not been addressed)

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