[DOC] Fix double-word typos in commentsv4.0.0-preview3

Found via `grep` for repeated words.

* set.c: Fix "or or"
* include/ruby/internal/symbol.h: Fix "is is"
* include/ruby/internal/ctype.h: Fix "in in"

1 files changed, 1 insertions, 1 deletions

diff --git a/set.c b/set.c
index 8bd8ae5632..734a6ecaea 100644
--- a/set.c
+++ b/set.c
@@ -1766,7 +1766,7 @@ set_i_disjoint(VALUE set, VALUE other)
  *    set <=> other -> -1, 0, 1, or nil
  *
  *  Returns 0 if the set are equal, -1 / 1 if the set is a
- *  proper subset / superset of the given set, or or nil if
+ *  proper subset / superset of the given set, or nil if
  *  they both have unique elements.
  */
 static VALUE