docs : Fix duplicated file extension in test command (#11935)

docs : Fix duplicated file extension in test command (#11935)

This commit fixes an issue in the llama.cpp project where the command for testing the llama-server object contained a duplicated file extension. The original command was:
./tests.sh unit/test_chat_completion.py.py -v -x
It has been corrected to:
./tests.sh unit/test_chat_completion.py -v -x
This change ensures that the test script correctly locates and executes the intended test file, preventing test failures due to an incorrect file name.