doc: Fix typo in admin-guide/cifs/introduction.rst

This patch corrects a spelling error specifically
the word "supports" was misspelled "suppors".

No functional changes are made by this patch; it
only improves the accuracy and readability of the
documentation.

Signed-off-by: Kendra Moore <kendra.j.moore3443@gmail.com>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20240312084753.27122-1-kendra.j.moore3443@gmail.com>