Update _orca.py (#1840)

Currently, this link guides user to [](https://github.com/plotly/orca.) instead of [](https://github.com/plotly/orca)

Author: StandbyMe

Diff for: packages/python/plotly/plotly/io/_orca.py

@@ -1001,7 +1001,7 @@ def validate_executable():
     $ conda install -c plotly plotly-orca
 
 Alternatively, see other installation methods in the orca project README at
-https://github.com/plotly/orca.
+https://github.com/plotly/orca
 
 After installation is complete, no further configuration should be needed.