pdb docs: workaround for double semicolon in strings (#17011)

see gotcha/ipdb#172

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

Author: gotcha

Doc/library/pdb.rst

@@ -233,7 +233,8 @@ Multiple commands may be entered on a single line, separated by ``;;``.  (A
 single ``;`` is not used as it is the separator for multiple commands in a line
 that is passed to the Python parser.)  No intelligence is applied to separating
 the commands; the input is split at the first ``;;`` pair, even if it is in the
-middle of a quoted string.
+middle of a quoted string. A workaround for strings with double semicolons
+is to use implicit string concatenation ``';'';'`` or ``";"";"``.
 
 .. index::
    pair: .pdbrc; file