pt-k8s-debug-collector integration of pg_gather requires croping first line of the output file

It has been reported that the first line of the output file contains extra information like

stderr: , stdout: ...

When the data is collected using pt-k8s-debug-collector.

All extra characters before the pg_gather output need to be removed from the final file.

The first line of the file need to be starting with a line

\set ver XX 

Where XX is an integer showing the version number