Bug 251991: Convert dialogs of the PSM to <dialog>

r=neil, sr=jst

suite/locales/en-US/chrome/common/help/cert_dialog_help.xhtml

@@ -408,8 +408,8 @@ were encrypted with your corresponding public key.</p>
 <ul>
   <li><strong>View Certificate:</strong> To examine information about the certificate,
     including its validity period, click View Certificate.</li>
-  <li><strong>OK:</strong> If you have reason to believe the certificate&apos;s expiration is an
-    inadvertent error, you may choose to click OK to accept the certificate anyway for this
+  <li><strong>Continue:</strong> If you have reason to believe the certificate&apos;s expiration is an
+    inadvertent error, you may choose to click Continue to accept the certificate anyway for this
     session, and let the webmaster for the site know about the problem.
     <p>Be cautious about any actions you take while you are visiting the site.</p></li>
   <li><strong>Cancel:</strong> If you suspect that there may be a significant problem and you