Remove a redundant conditional in HTMLIFrameElement

A previous review comment [*] pointed out this conditional doesn't do
anything, but it looks like I marked the comment as resolved without
addressing it.

[*]
https://chromium-review.googlesource.com/c/chromium/src/+/2116014/11/third_party/blink/renderer/core/html/html_iframe_element.cc#270

R=jbroman

Bug: 1062396
Change-Id: I88169236039269435d0c0499e3324f5d3958bfb4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2131410Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: David Van Cleve <davidvc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755334}

third_party/blink/renderer/core/html/html_iframe_element.cc

@@ -266,9 +266,7 @@ void HTMLIFrameElement::ParseAttribute(
       UpdateRequiredPolicy();
     }
   } else if (name == html_names::kTrusttokenAttr) {
-    if (trust_token_ != value) {
-      trust_token_ = value;
-    }
+    trust_token_ = value;
   } else {
     // Websites picked up a Chromium article that used this non-specified
     // attribute which ended up changing shape after the specification process.