docs(frontend): Fixed typo in command

[ved-kashyap-samsung]

SUMMARY

There is a typo in command with extra tick in command export NODE_OPTIONS=--no-experimental-fetch which gives error. So, removed typo in this PR.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

• Try fresh installation
• after superset/superset-frontend when you will do npm run dev-server , then following error will come.

Error: You must provide the URL of lib/mappings.wasm by calling SourceMapConsumer.initialize({ 'lib/mappings.wasm': ... }) before using SourceMapConsumer at readWasm (/home/test/superset_setup/superset/superset-frontend/node_modules/react-hot-loader/node_modules/source-map/lib/read-wasm.js:8:13) at wasm (/home/test/superset_setup/superset/superset-frontend/node_modules/react-hot-loader/node_modules/source-map/lib/wasm.js:25:16) at /home/test/superset_setup/superset/superset-frontend/node_modules/react-hot-loader/node_modules/source-map/lib/source-map-consumer.js:264:14

• Above error was resolved by doing following:

export NODE_OPTIONS=--no-experimental-fetch

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

[ved-kashyap-samsung]

@rusackas Can you please review.