Update regex to allow BOF config prompt on SROS

[kaelemc]

Description

This is a fairly simple change which improves the SROS regex allowing for:

• Allow for BOF configuration mode in the MD-CLI prompt.

We rely on it for hellt/vrnetlab#297 😄

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Tested with the vrnetlab code here. Basically, applies a bootstrap config to the vSIM using Scrapli via telnet.

• Tested with 24.10.R1

Here are some regex101 links to display the matching:

old	new

Please let me know if I missed anything or if you need any more info!

Checklist:

• My code follows the style guidelines of this project (no GitHub actions complaints! run make lint before
  committing!)
• I have commented my code, pydocstyle and darglint are happy, docstrings are in google docstring format, and all
  docstrings include a summary, args, returns and raises fields (even if N/A)
• I have added tests that prove my fix is effective or that my feature works, if adding "functional" tests please
  note if there are any considerations for the vrnetlab setup
• New and existing unit tests pass locally with my changes

[carlmontanari]

LGTM, thanks @kaelemc :D

[kaelemc]

Thanks!