Fix input name in README

[osreboot]

Changes

After running this action I got the error:

Unexpected input(s) 'firstDepotId', valid inputs are ['username', 'password', 'configVdf', 'ssfnFileName', 'ssfnFileContents', 'appId', 'firstDepotIdOverride', 'buildDescription', 'rootPath', 'depot1Path', 'depot2Path', 'depot3Path', 'depot4Path', 'depot5Path', 'depot6Path', 'depot7Path', 'depot8Path', 'depot9Path', 'releaseBranch']

...it looks like the input parameter listed on the README isn't correct 🤔

Checklist

• Read the contribution guide and accept the code of conduct
• Readme (updated or not needed)
• Tests (added, updated or not needed)

[webbertakken]

Thank you!