Fix link to moved section (#1282)

Author: mscwilson

docs/sources/trackers/javascript-trackers/web-tracker/migration-guides/v3-to-v4-migration-guide/index.md

@@ -146,7 +146,7 @@ In v4, if not configured explicitly, the setting will now default to `false` if
 
 If your Collector is hosted behind a Web Application Firewall and custom entities/events include content that may be classified as risky (e.g. content containing HTML code) this may trigger false positives and cause the events to be rejected by the firewall; re-enabling base64 encoding should obfuscate the payload again and allow successful delivery.
 
-Per the [tracker protocol](/docs/sources/trackers/snowplow-tracker-protocol/index.md), the payload fields used for base-64-encoded data differs from plain JSON-encoded data: When upgrading to v4, plugins or tests relying on payload data being in `cx` or `ue_px` may now require updating to check the non-base64-encoded equivalents in `co` and `ue_pr`. Tracker protocol-compliant processors such as the Enricher should already support both fields and require no changes.
+Per the [tracker protocol](/docs/events/index.md), the payload fields used for base-64-encoded data differs from plain JSON-encoded data: when upgrading to v4, plugins or tests relying on payload data being in `cx` or `ue_px` may now require updating to check the non-base64-encoded equivalents in `co` and `ue_pr`. Tracker protocol-compliant processors such as the Enricher should already support both fields and require no changes.
 
 ### Dropped support for older browsers