Minor grammar improvement to io documentation. (GH-10329)

Independently of -> Independent of

Doc/library/io.rst

@@ -31,7 +31,7 @@ be used for each of them.  A concrete object belonging to any of these
 categories is called a :term:`file object`.  Other common terms are *stream*
 and *file-like object*.
 
-Independently of its category, each concrete stream object will also have
+Independent of its category, each concrete stream object will also have
 various capabilities: it can be read-only, write-only, or read-write. It can
 also allow arbitrary random access (seeking forwards or backwards to any
 location), or only sequential access (for example in the case of a socket or