Remove transformers from pipeline.yaml

Remove transformers from pipeline.yaml

This change removes usage of transformers from pipeline.yaml because
support of transofermer was already removed from ceilometer[1].

[1] 9db5c6c9bfc66018aeb78c4a262e1bfa9b326798

Backport note:
This backport patch includes the subsequent change[2] to fix the wrong
file mentioned in the release note file.

[2] d27fbd3fed472a51670393a4a295ba6b16a35bea

Closes-Bug: #1912345
Change-Id: Ibadafdf86f5ce581c9084a5e00784eefa7d28cab
(cherry picked from commit 5b8f5d0490f43f43a62cee9718c75290e30473cf)
(cherry picked from commit 815d7033dbe6f5c3dde1128ce6aecc4048eb09cb)
(cherry picked from commit ed9563b63fdc85f16b95f9daee311f26e21a391e)