binascii docs: strict_mode parameter is keyword-only (GH-93055)

See 35b98e3

Co-authored-by: Adam Turner <[email protected]>
(cherry picked from commit ac718d3)

Co-authored-by: Jelle Zijlstra <[email protected]>

Author: miss-islington

Doc/library/binascii.rst

@@ -49,7 +49,7 @@ The :mod:`binascii` module defines the following functions:
       Added the *backtick* parameter.
 
 
-.. function:: a2b_base64(string, strict_mode=False)
+.. function:: a2b_base64(string, /, *, strict_mode=False)
 
    Convert a block of base64 data back to binary and return the binary data. More
    than one line may be passed at a time.