[stdlib] Fix mismatched constant name in static func == doc

[Jager-yoo]

• I've found a mismatched constant name in static func == example. 😄
• Given the context, it should be numberToMatch, not numberToFind.

  /// You can also use this operator to compare a non-optional value to an
  /// optional that wraps the same type. The non-optional value is wrapped as an
  /// optional before the comparison is made. In the following example, the
  /// `numberToMatch` constant is wrapped as an optional before comparing to the
  /// optional `numberFromString`:

     let **numberToFind**: Int = 23  // → this should be *numberToMatch*
     let numberFromString: Int? = Int("23")      // Optional(23)
     if **numberToFind** == numberFromString {  // → this should be *numberToMatch*
         print("It's a match!")
     }
     // Prints "It's a match!"

[CodaFi]

Thanks

@swift-ci smoke test and merge