mark the Character extension as fileprivate

Author: WowbaggersLiquidLunch

Sources/SymbolKit/SymbolGraph/SemanticVersion/Prerelease.swift

@@ -145,7 +145,7 @@ extension SymbolGraph.SemanticVersion.Prerelease.Identifier: CustomStringConvert
 
 // MARK: - Validating Identifiers
 
-extension Character {
+fileprivate extension Character {
     /// A Boolean value indicating whether this character is allowed in a semantic version's identifier.
     internal var isAllowedInSemanticVersionIdentifier: Bool {
         isASCII && (isLetter || isNumber || self == "-")