clean up bullet concatenation

Author: LePips

Plugins/PluginsShared/PluginError.swift

@@ -37,7 +37,7 @@ enum PluginError: Swift.Error, CustomStringConvertible, LocalizedError {
             let targetNames = targetNames.joined(separator: ", ", lastSeparator: " and ")
             return "Found no targets with names \(targetNames)."
         case .fileErrors(let fileErrors):
-            return "Issues with required files:\n\(fileErrors.map { $0 .description.prepended("- ") }.joined(separator: "\n"))."
+            return "Issues with required files:\n\(fileErrors.map { "- " + $0 .description }.joined(separator: "\n"))."
         }
     }
 

Plugins/PluginsShared/PluginUtils.swift

@@ -97,9 +97,3 @@ extension Array where Element == String {
         return "\(self.dropLast().joined(separator: separator))\(lastSeparator)\(self.last!)"
     }
 }
-
-extension String {
-    func prepended(_ prefix: String) -> String {
-        return prefix + self
-    }
-}