Small typo in the instruction comments of WithColor header

[dseynhae]

Summary

Fix a small but misleading/confusing typo in the comments (which shows up in the doxygen documentation):

Black -> BLACK (the enumeration is case-sensitive).

[JDevlieghere]

Thank you, LGTM! Please let me know if you need someone to land this for you.

[dseynhae]

In D151598#4381644, @JDevlieghere wrote:

Thank you, LGTM! Please let me know if you need someone to land this for you.

@JDevlieghere :

I'm not in a position yet where I can commit straight to main... Can you assign this to an appropriate resource?

llvm/include/llvm/Support/WithColor.h

public:
   using AutoDetectFunctionType = bool (*)(const raw_ostream &OS);
 
   /// To be used like this: WithColor(OS, HighlightColor::String) << "text";
   /// @param OS The output stream
   /// @param S Symbolic name for syntax element to color
   /// @param Mode Enable, disable or compute whether to use colors.
   WithColor(raw_ostream &OS, HighlightColor S,
             ColorMode Mode = ColorMode::Auto);
-  /// To be used like this: WithColor(OS, raw_ostream::Black) << "text";
+  /// To be used like this: WithColor(OS, raw_ostream::BLACK) << "text";
   /// @param OS The output stream
   /// @param Color ANSI color to use, the special SAVEDCOLOR can be used to
   /// change only the bold attribute, and keep colors untouched
   /// @param Bold Bold/brighter text, default false
   /// @param BG If true, change the background, default: change foreground
   /// @param Mode Enable, disable or compute whether to use colors.
   WithColor(raw_ostream &OS,
             raw_ostream::Colors Color = raw_ostream::SAVEDCOLOR,