update install instructions

doc/source/index.rst

@@ -16,11 +16,11 @@ Installation
 
 The samsam package can be installed using the pip utility
 
-``pip install --extra-index-url https://obswww.unige.ch/~delisle samsam``
+``pip install samsam``
 
 and upgraded with
 
-``pip install --extra-index-url https://obswww.unige.ch/~delisle samsam --upgrade``
+``pip install samsam --upgrade``
 
 Example
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