[DOC] Fix hash style for Array#flatten!

Author: peterzhu2118

array.c

@@ -6747,16 +6747,16 @@ flatten(VALUE ary, int level)
  *  With non-negative integer argument +depth+, flattens recursively through +depth+ levels:
  *
  *    a = [ 0, [ 1, [2, 3], 4 ], 5, {foo: 0}, Set.new([6, 7]) ]
- *    a                   # => [0, [1, [2, 3], 4], 5, {:foo=>0}, #<Set: {6, 7}>]
- *    a.dup.flatten!(1)   # => [0, 1, [2, 3], 4, 5, {:foo=>0}, #<Set: {6, 7}>]
- *    a.dup.flatten!(1.1) # => [0, 1, [2, 3], 4, 5, {:foo=>0}, #<Set: {6, 7}>]
- *    a.dup.flatten!(2)   # => [0, 1, 2, 3, 4, 5, {:foo=>0}, #<Set: {6, 7}>]
- *    a.dup.flatten!(3)   # => [0, 1, 2, 3, 4, 5, {:foo=>0}, #<Set: {6, 7}>]
+ *    a                   # => [0, [1, [2, 3], 4], 5, {foo: 0}, #<Set: {6, 7}>]
+ *    a.dup.flatten!(1)   # => [0, 1, [2, 3], 4, 5, {foo: 0}, #<Set: {6, 7}>]
+ *    a.dup.flatten!(1.1) # => [0, 1, [2, 3], 4, 5, {foo: 0}, #<Set: {6, 7}>]
+ *    a.dup.flatten!(2)   # => [0, 1, 2, 3, 4, 5, {foo: 0}, #<Set: {6, 7}>]
+ *    a.dup.flatten!(3)   # => [0, 1, 2, 3, 4, 5, {foo: 0}, #<Set: {6, 7}>]
  *
  *  With +nil+ or negative argument +depth+, flattens all levels:
  *
- *    a.dup.flatten!     # => [0, 1, 2, 3, 4, 5, {:foo=>0}, #<Set: {6, 7}>]
- *    a.dup.flatten!(-1) # => [0, 1, 2, 3, 4, 5, {:foo=>0}, #<Set: {6, 7}>]
+ *    a.dup.flatten!     # => [0, 1, 2, 3, 4, 5, {foo: 0}, #<Set: {6, 7}>]
+ *    a.dup.flatten!(-1) # => [0, 1, 2, 3, 4, 5, {foo: 0}, #<Set: {6, 7}>]
  *
  *  Related: Array#flatten;
  *  see also {Methods for Assigning}[rdoc-ref:Array@Methods+for+Assigning].