Fix the regex for setting topic

The regex did not support the use of a `:` and a `#` in the bug
identification line. The updated regex now will support bug
identification lines that look like `Closes-Bug: #12345`.

Co-Authored-By: Nicolas Simonds <nic@metacloud.com>
Change-Id: Ie5edd9a04fe714302f06b2df2c4c134a2ef2316a
Merge "Fix the regex for setting topic"