fix: clean translations before pulling them

[kdmccormick]

Description

If one is using a bind-mounted edx-platform directory, they may already have pulled translations. This will cause the Docker build to fail with:

CommandError: "/openedx/edx-platform/conf/plugins-locale/plugins" should be empty before running atlas pull.

To fix this, we simply clean out the edx-platform translation target directories before pulling in the Dockerfile.

Blockers

• chore: clean_translations refactored into separate makefile target | FC-0012 openedx/edx-platform#34428
• build: clean_translations without .git openedx/edx-platform#34429

Extra discussion

https://openedx.slack.com/archives/C04R6TUJB7T/p1711482071806759?thread_ts=1711478732.261049&cid=C04R6TUJB7T

[kdmccormick]

Ack, this fails with:

 > [production 18/34] RUN make clean_translations:                                  
0.194 git clean -fdX conf/locale  # Removes core edx-platform translations but keeps Esperanto (eo) test translations
0.196 fatal: not a git repository (or any of the parent directories): .git
0.196 make: *** [Makefile:57: clean_translations] Error 128

This is happening because we intentionally avoid copying .git in at this layer, as that would bloat the layer and cause its cache to be invalidated with any git state change whatsoever.

I'm going to turn this into a draft, a propose an alternate upstream implementation of make clean_translations which doesn't rely on git.

UPDATE: the amended edx-platform PR is here: https://github.com/openedx/edx-platform/pull/34429/files

[kdmccormick]

The edx-platform PR linked above merged, so make clean_translations now works in the Dockerfile.

I tested this locally and confirmed that it fixes the error.