Fixes duplicated word (#102623)

In line 1627, the end of the sentence reads "only that that it may be." but it should read "only that it may be" (or alternatively "only that that may be").

Co-authored-by: Hugo Gabriel Eyherabide <[email protected]>

Author: gvanrossum

Doc/library/subprocess.rst

@@ -1622,7 +1622,7 @@ that.
 It is safe to set these to false on any Python version. They will have no
 effect on older versions when unsupported. Do not assume the attributes are
 available to read. Despite their names, a true value does not indicate that the
-corresponding function will be used, only that that it may be.
+corresponding function will be used, only that it may be.
 
 Please file issues any time you have to use these private knobs with a way to
 reproduce the issue you were seeing. Link to that issue from a comment in your