Fix Embedding test with ragged tensors on GPU.

[hertschuh]

The loss needs to not have any non-compilable op.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.58%. Comparing base (1ea81a1) to head (e7090e9).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21177   +/-   ##
=======================================
  Coverage   82.58%   82.58%           
=======================================
  Files         564      564           
  Lines       54359    54366    +7     
  Branches     8448     8448           
=======================================
+ Hits        44891    44898    +7     
  Misses       7393     7393           
  Partials     2075     2075           

Flag	Coverage Δ
keras	82.39% <100.00%> (+<0.01%)	⬆️
keras-jax	63.80% <100.00%> (-0.01%)	⬇️
keras-numpy	58.92% <25.00%> (-0.01%)	⬇️
keras-openvino	32.92% <25.00%> (+<0.01%)	⬆️
keras-tensorflow	64.21% <100.00%> (-0.01%)	⬇️
keras-torch	63.89% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[fchollet]

LGTM, thanks for the fix!