docs: Fix function name trailing double-()s

I noticed a double-() in the deprecated.rst rendering today. Fix that
one and two others in the Documentation/ tree.

Acked-by: "Paul E. McKenney" <paulmck@kernel.org> # For RCU
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200817233207.4083538-1-keescook@chromium.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
index 4a9aa4f..918e32d 100644
--- a/Documentation/process/deprecated.rst
+++ b/Documentation/process/deprecated.rst
@@ -142,7 +142,7 @@
 (Users of strscpy() still needing NUL-padding should instead
 use strscpy_pad().)
 
-If a caller is using non-NUL-terminated strings, strncpy()() can
+If a caller is using non-NUL-terminated strings, strncpy() can
 still be used, but destinations should be marked with the `__nonstring
 <https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html>`_
 attribute to avoid future compiler warnings.