complex.c: doc fix

* complex.c: [DOC] fix grammar and typo.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60569 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

complex.c

@@ -1353,8 +1353,8 @@ nucomp_inspect(VALUE self)
  * call-seq:
  *    cmp.finite?  ->  true or false
  *
- * Returns +true+ if +cmp+'s magnitude is finite number,
- * oterwise returns +false+.
+ * Returns +true+ if +cmp+'s magnitude is a finite number,
+ * otherwise returns +false+.
  */
 static VALUE
 rb_complex_finite_p(VALUE self)