modified regex example to fix invalid escape strings warning

[17jmumford]

Details

The regex example in regex_match.py was using \d in a regular string, which triggers a Python SyntaxWarning: invalid escape sequence '\d' when running an application using Opik. This warning occurs because Python interprets backslashes in regular strings as escape sequences, and \d is not a valid escape sequence.

Issues

Resolves #1163

Testing

This change properly escapes the backslashes in the regular string while maintaining identical regex matching functionality. The double backslash ensures Python correctly passes a single backslash to the regex engine.

• Verified that the warning no longer appears when running the application
• Confirmed that the regex pattern continues to match the same strings as before. Doesn't really matter since it's just an example

[alexkuzmik]

@17jmumford thanks, good catch!