chore: applying PR rewording suggestion

Co-authored-by: Copilot <[email protected]>

Author: DevTKSS

src/AspNet.Security.OAuth.Etsy/EtsyAuthenticationOptions.cs

@@ -55,7 +55,7 @@ public override void Validate()
         {
             // HACK We want all of the base validation except for ClientSecret,
             // so rather than re-implement it all, catch the exception thrown
-            // for that being null and only throw if we aren't using public access type.
+            // for that being null and only throw if we aren't using PKCE, as Etsy's OAuth implementation does not require a client secret when using PKCE (Proof Key for Code Exchange).
             // This does mean that three checks have to be re-implemented
             // because the won't be validated if the ClientSecret validation fails.
             base.Validate();