[Diagnostics] Remove rendering of educational notes to the terminal

We're moving over to a model where we provide direct links to educational notes /
diagnostic group notes whenever relevant. Rendering the Markdown from these
files to the terminal is less relevant with this approach, so remove it from the
compiler.

include/swift/Frontend/PrintingDiagnosticConsumer.h

@@ -32,14 +32,10 @@ namespace swift {
 class PrintingDiagnosticConsumer : public DiagnosticConsumer {
   llvm::raw_ostream &Stream;
   bool ForceColors = false;
-  bool PrintEducationalNotes = false;
   bool EmitMacroExpansionFiles = false;
   bool DidErrorOccur = false;
   DiagnosticOptions::FormattingStyle FormattingStyle =
       DiagnosticOptions::FormattingStyle::LLVM;
-  // Educational notes which are buffered until the consumer is finished
-  // constructing a snippet.
-  SmallVector<std::string, 1> BufferedEducationalNotes;
   bool SuppressOutput = false;
 
 #if SWIFT_BUILD_SWIFT_SYNTAX
@@ -65,10 +61,6 @@ public:
     llvm::sys::Process::UseANSIEscapeCodes(true);
   }
 
-  void setPrintEducationalNotes(bool ShouldPrint) {
-    PrintEducationalNotes = ShouldPrint;
-  }
-
   void setFormattingStyle(DiagnosticOptions::FormattingStyle style) {
     FormattingStyle = style;
   }