CI: Improve warning when no pandas dev version installed when running stubtest

[phofl]

see #48240 (review)

[samrao1997]

@phofl Could you explain what the #current condition would be if pandas version is false?

[mroeschke]

#current condition just means the logic that already exists in that if block

[ambujpawar]

This looks something I can do. Can I take this up?

[phofl]

Sure

[ambujpawar]

take