Update repo url for python system metrics (#614)

System metrics were moved to a separate branch in open-telemetry/opentelemetry-python-contrib#312

Author: RobertRosca

Diff for: content/en/registry/instrumentation-python-system-metrics.md

@@ -6,7 +6,7 @@ language: python
 tags:
   - python
   - instrumentation
-repo: https://github.com/open-telemetry/opentelemetry-python-contrib/tree/main/instrumentation/opentelemetry-instrumentation-system-metrics
+repo: https://github.com/open-telemetry/opentelemetry-python-contrib/tree/metrics/instrumentation/opentelemetry-instrumentation-system-metrics
 license: Apache 2.0
 description: Instrumentation to collect system performance metrics.
 authors: OpenTelemetry Authors