docs: fix typo (open-telemetry#543)

Author: lizthegrey

opentelemetry-auto-instrumentation/src/opentelemetry/auto_instrumentation/__init__.py

@@ -24,5 +24,5 @@
 
 The code in ``program.py`` needs to use one of the packages for which there is
 an OpenTelemetry extension. For a list of the available extensions please check
-`here <https://opentelemetry-python.readthedocsio/>`_.
+`here <https://opentelemetry-python.readthedocs.io/>`_.
 """