Fixes#123-dead code cb after return

[Sanskar12G]

Fixes : #123
Problem
In both translations and pot task functions, cb() was placed
after a return statement making it dead code that can never be
executed.

Fix
Since both functions return a stream, Gulp 4 handles task completion
automatically. Removed the unnecessary 'cb' parameter and dead cb()
calls from both functions.

Changes

• gulpfile.js: removed 'cb' parameter from translations function
• gulpfile.js: removed 'cb' parameter and dead 'cb()' from pot function

[robertodauria]

Thanks for the contribution, but we require prior coordination with a maintainer before opening PRs. Please also check existing issues and PRs — the gulpfile is being replaced as part of the build system modernization tracked in #83.

Please see our engagement requirements.

Closing this PR.