Adhere to naming convention

Author: ghostbuster91

compiler/src/dotty/tools/dotc/reporting/MessageKind.scala

@@ -38,6 +38,6 @@ enum MessageKind:
       case PatternMatchExhaustivity => "Pattern Match Exhaustivity"
       case MatchCaseUnreachable => "Match case Unreachable"
       case PotentialIssue => "Potential Issue"
-      case UnusedSymbol => "Unused symbol"
+      case UnusedSymbol => "Unused Symbol"
       case kind => kind.toString
 end MessageKind

compiler/test-resources/repl/i18383

@@ -4,7 +4,7 @@ scala> import scala.collection.*
 
 scala> class Foo { import scala.util.*; println("foo") }
 1 warning found
--- [E195] Unused symbol Warning: -----------------------------------------------
+-- [E195] Unused Symbol Warning: -----------------------------------------------
 1 | class Foo { import scala.util.*; println("foo") }
   |                               ^
   |                               unused import