Remove dead O'Reilly webinar link from README

The README linked to a June 2017 O'Reilly webinar whose events microsite has since been retired, so the page returns 403 and fails the PR link checker on every README change. Drop the link; the rest of the Pattern Discussion Webinar entry stands on its own.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EDwBfCivCNdKJA2BexAizd

Author: rrrutledge

README.md

@@ -135,7 +135,7 @@ Patterns are a way of describing a repeatable, proven solution to a problem with
 Patterns can provide a way for the InnerSource Commons participants to concisely share information, improving the practice of InnerSource. Patterns are divided into Title, Problem Statement, Context, Forces, and Solutions as their main sections.
 
 * [What are patterns?](https://bit.ly/innersource_patterns_videos) - Watch a set of 2-5 min videos explaining InnerSource Patterns
-* [Pattern Discussion Webinar](https://youtu.be/i-0IVhfRVFU?t=1479) - We held a webinar 2017-03-16 to have a live discussion on a donut pattern (go to [24:40](https://youtu.be/i-0IVhfRVFU?t=1479) for the discussion). This is an illustration of the review process we follow. Also see the [June 1, 2017 O'Reilly Webinar on InnerSource Patterns](http://www.oreilly.com/pub/e/3884).
+* [Pattern Discussion Webinar](https://youtu.be/i-0IVhfRVFU?t=1479) - We held a webinar 2017-03-16 to have a live discussion on a donut pattern (go to [24:40](https://youtu.be/i-0IVhfRVFU?t=1479) for the discussion). This is an illustration of the review process we follow.
 * [Pattern Template File](meta/pattern-template.md) - View a skeleton InnerSource pattern to get an idea on what goes into a new pattern!
 * [Introduction to InnerSource Patterns (2016 Fall Summit)](https://drive.google.com/open?id=0B7_9iQb93uBQbnlkdHNuUGhpTXc) - *Tim Yao and Padma Sudarsan* (PDF). Detailed pattern background and examples -- Get a detailed understanding of why and how to interact with our patterns. Also see the [Introduction to InnerSource Patterns (2017 Fall Summit)](https://drive.google.com/open?id=0B7_9iQb93uBQWmYwMFpyaGh4OFU) *Tim Yao and Bob Hanmer* (PDF).
 * A scientific look at how to write patterns: [A pattern language for pattern writing](http://hillside.net/index.php/a-pattern-language-for-pattern-writing), Meszaros and Doble