TL: minor doc correction (#260)

Author: tlunet

README.md

@@ -46,7 +46,7 @@ environment. For this, `pySDC` ships with environment files
 which can be found in the folder `etc/`. Use these as e.g.
 
 ``` bash
-conda env create --yes -f etc/environment-base.yml
+conda env create -f etc/environment-base.yml
 ```
 
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