Fix doc comment (#632)

Author: valeriyvan

Sources/SnapshotTesting/Snapshotting/Description.swift

@@ -1,5 +1,5 @@
 extension Snapshotting where Format == String {
-  /// A snapshot strategy that captures a value's textual description from `String`'s `init(description:)`
+  /// A snapshot strategy that captures a value's textual description from `String`'s `init(describing:)`
   /// initializer.
   public static var description: Snapshotting {
     return SimplySnapshotting.lines.pullback(String.init(describing:))