Change kaleido conda channel to plotly since it most likely won't be available on conda-forge initially

Author: jonmmease

README.md

@@ -146,7 +146,7 @@ $ pip install -U kaleido
 
 or conda.
 ```
-$ conda install -c conda-forge kaleido
+$ conda install -c plotly kaleido
 ``` 
 
 ### Static Image Export with Orca

doc/python/static-image-export.md

@@ -49,7 +49,7 @@ $ pip install -U kaleido
 
 or conda.
 ```
-$ conda install -c conda-forge kaleido
+$ conda install -c plotly kaleido
 ``` 
 
 #### Install Dependencies (Orca)