[2.7] bpo-33877: Remove UNIX qualification for running complete programs (GH-7744)

The statement is true for Windows (and macOS) also..
(cherry picked from commit c9d43c7)

Co-authored-by: Andrés Delfino <[email protected]>

Author: andresdelfino

Doc/reference/toplevel_components.rst

@@ -51,11 +51,11 @@ a complete program; each statement is executed in the namespace of
    single: command line
    single: standard input
 
-Under Unix, a complete program can be passed to the interpreter in three forms:
-with the :option:`-c` *string* command line option, as a file passed as the
-first command line argument, or as standard input. If the file or standard input
-is a tty device, the interpreter enters interactive mode; otherwise, it executes
-the file as a complete program.
+A complete program can be passed to the interpreter
+in three forms: with the :option:`-c` *string* command line option, as a file
+passed as the first command line argument, or as standard input. If the file
+or standard input is a tty device, the interpreter enters interactive mode;
+otherwise, it executes the file as a complete program.
 
 
 .. _file-input: