Partially reverse "Make language slug available via session metadata"

[minhaminha]

Product Description

Users will still be able to reference the current screen's language slug using instance('commcaresession')/session/context/applanguage

Improvement over #1441

Associated dimagi/formplayer#1630

Technical Summary

Shubham pointed out there is an existing function Localization.getCurrentLocale() that eliminates the need for convoluted ways to pass along the locale value from the initial BaseResponseBean.

Safety Assurance

Safety story

Tested locally and on staging. No data impact as the metadata refreshes with every navigation request.

QA Plan

Will have delivery try out their tests once more before merging.

Special deploy instructions

• This PR can be deployed after merge with no further considerations.

Rollback instructions

• This PR can be reverted after deploy with no further considerations.

Review

• The set of people pinged as reviewers is appropriate for the level of risk of the change.

Duplicate PR

Automatically duplicate this PR as defined in contributing.md.