Update README.rst (#2111)

Co-authored-by: Leighton Chen <lechen@microsoft.com>

Author: awhlam

instrumentation/opentelemetry-instrumentation-tortoiseorm/README.rst

@@ -19,5 +19,5 @@ References
 ----------
 
 * `OpenTelemetry Project <https://opentelemetry.io/>`_
-* `Tortoise ORM <https://tortoise-orm.readthedocs.io/en/latest/>`_
+* `Tortoise ORM <https://tortoise.github.io/>`_
 * `OpenTelemetry Python Examples <https://github.com/open-telemetry/opentelemetry-python/tree/main/docs/examples>`_