maint: Use Octave coding conventions for cuddling parentheses in doc directory * OctaveFAQ.texi, basics.txi, container.txi, contrib.txi, diagperm.txi, diffeq.txi, dynamic.txi, errors.txi, eval.txi, expr.txi, func.txi, geometry.txi, interp.txi, intro.txi, numbers.txi, oop.txi, plot.txi, poly.txi, quad.txi, set.txi, sparse.txi, stmt.txi, testfun.txi, vectorize.txi, refcard.tex: Use Octave coding conventions for cuddling parentheses.

--- a/doc/interpreter/contrib.txi
+++ b/doc/interpreter/contrib.txi
@@ -331,7 +331,7 @@
 @example
 @group
 if (isvector (a))
-  s = sum(a);
+  s = sum (a);
 endif
 @end group
 @end example