[gen_l10n] Remove redundant tests

[shihaohong]

Description

Since integration tests were introduced for gen_l10n, some of the unit tests are redundant since the new integration test better tests the correct behavior. This PR simply removes the redundant testing.

Related Issues

n/a

Tests

I added the following tests:

• Redundant tests were removed in this PR.

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Breaking Change

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[HansMuller]

We should land another PR that simplifies (refactors) the remaining tests so that the code is easier to read.

[HansMuller]

I assume this is viewed as redundant because the integration tests rely on being able to write to their "happy path" :-).