Remove unneeded environment variable

[jbischof]

Setting KERAS_BACKEND should be enough to trigger Keras Core usage

[jbischof]

/gcbrun

[ianstenbit]

toxic_env 😭

[jbischof]

Is there any way to check that the GCB tests ran as intended @ianstenbit? I can't see any print statements about the backend.

[ianstenbit]

As-is on this branch, the GCB tests ran the normal test suite (just three times)

You can see one run result here: https://pantheon.corp.google.com/cloud-build/builds/dd860e52-ebe6-4b93-b794-96f1d70cd092;step=5?jsmode=o&project=keras-team-test

So this is all set.

[jbischof]

Right, but do we need to check that the KERAS_BACKEND var was sufficient to trigger different backends instead of testing tf.keras over and over?

[ianstenbit]

Right, but do we need to check that the KERAS_BACKEND var was sufficient to trigger different backends instead of testing tf.keras over and over?

Oh I see -- yes, right now this just triggered tf.keras over and over for the GCB tests (that's expected, because #1935 isn't done). For the non-GCB tests, we can tell that keras_core is being tested because some tests (e.g. the RCNN tests) are skipped on these CI runs, which is only true for Keras Core