Fix typo removeSuffix -> removedSuffix

In StringExtension.swift,
`mutating func removeSuffix(_ suffix: String)` and
`func removeSuffix(_ suffix: String) -> String` are confusing, while
`mutating func removePrefix(_ prefix: String)` and
`func removedPrefix(_ prefix: String)` are properly named.

Author: v6x-junseok-lee

Sources/SparrowKit/Foundation/StringExtension.swift

@@ -159,7 +159,7 @@ public extension String {
 
      - parameter suffix: String which need remove.
      */
-    func removeSuffix(_ suffix: String) -> String {
+    func removedSuffix(_ suffix: String) -> String {
         if self.hasSuffix(suffix) {
             return String(dropLast(suffix.count))
         } else {