fix: remove messagesDir for babel-react-intl 8

[leangseu-edx]

The support for messageDir has been drop. formatjs/formatjs@47ca556

There should be a future plan use babel-plugin-formatjs instead because babel-react-intl has already been archived and moved.

[adamstankiewicz]

@leangseu-edx What is the consequence of removing messagesDir? How will our i18n process still function without it, if this is the only change? Is there a way we can ensure we stay on a version of babel-plugin-react-intl that supports messagesDir for now?

For example, I believe the path given to messagesDir is referenced in frontend-app-learning's Makefile around defining the i18n-related Make targets (source).

There should be a future plan use babel-plugin-formatjs instead because babel-react-intl has already been archived and moved.

@leangseu-edx The migration from babel-react-intl to babel-plugin-formatjs is something we prioritized with FED-BOM and looks to still be in progress (issue and PR).