Dear Jitendra,
No need to generate new workflow version for mail text. But you can also generate new version for your reference and do the changes and capture in TR and move to PRD.
Note : For safer side better do syntax check in PRD. Go to SWDD in PRD and enter your WF number and do syntax check.. if any error shows... then capture those missing things from DEV TR and Move to PRD and activate in PRD using the prgm RSWDACTIVATE.
Thanks,
Anand.