Remove non existing 'coretex_m_backend' target

[AdrianLundell]

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

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❌ 4 New Failures

As of commit c24d6c9 with merge base d17ff74 ():

NEW FAILURES - The following jobs have failed:

• pull / test-openvino-linux / linux-job (gh)
  RuntimeError: Command docker exec -t bd0368326a5853b653f7d51c7a298ed5f18493156eba5e878e695ee762b56e86 /exec failed with exit code 1
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 6a6121dcde2acdd9c72e7322de87aadc2e743f39367268524026828afe07de37 /exec failed with exit code 1
• pull / test-samsung-quantmodels-linux / linux-job (gh)
  RuntimeError: Command docker exec -t cd19f8c9dce914e36da63b5c390a771ca7c8daed15c648a3155a34654a287047 /exec failed with exit code 1
• Test CUDA Builds / test-models-cuda (resnet18) / linux-job (gh)
  RuntimeError: Command docker exec -t 2274f793e472a891a907e5e8204a03aa60d7f149389e392d4e6803e3425ba383 /exec failed with exit code 1

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