Remove @IBOutlet and @IBInspectable from UnusedDeclarationRule

This list was intended to be things that could have side effects from
being in IB, or just being dynamic, and therefore we cannot tell if they
are used or not. In the case of the 2 attributes I'm removing, they
could be used in IB, but if they aren't used in code, they should still
be considered dead.

Source/SwiftLintFramework/Rules/Lint/UnusedDeclarationRule.swift

@@ -201,7 +201,7 @@ private extension SwiftLintFile {
             // Skip declarations marked as @IBOutlet, @IBAction or @objc
             // since those might not be referenced in code, but only dynamically (e.g. Interface Builder)
             if let annotatedDecl = cursorInfo.annotatedDeclaration,
-                ["@IBOutlet", "@IBAction", "@objc", "@IBInspectable"].contains(where: annotatedDecl.contains) {
+                ["@IBAction", "@objc"].contains(where: annotatedDecl.contains) {
                 return nil
             }