update Python version support in docs (#2037)

Co-authored-by: Paul Ivanov <[email protected]>

Author: minrk

docs/source/install.rst

@@ -11,7 +11,7 @@ Installation
 Supported Python versions
 -------------------------
 
-Currently Python 3.7-3.9 is supported and tested by nbconvert.
+Currently Python 3.8-3.11 is supported and tested by nbconvert.
 
 Installing nbconvert
 --------------------