model-conversion : remove hardcoded /bin/bash shebangs [no ci] (#15765)

model-conversion : remove hardcoded /bin/bash shebangs [no ci] (#15765)

* model-conversion : remove hardcoded /bin/bash shebangs [no ci]

This commit updates the bash scripts to use env instead of using
hardcoded /bin/bash in the shebang line.

The motivation for this is that some systems may have bash installed
in a different location, and using /usr/bin/env bash ensures that
the script will use the first bash interpreter found in the user's
PATH, making the scripts more portable across different environments.

* model-conversion : rename script to .py [no ci]

This commit renames run-casual-gen-embeddings-org.sh to
run-casual-gen-embeddings-org.py to reflect its Python nature.