Add new agreed URLs to account data instead of overwriting

This changes terms account data storage to always add, rather than setting only
the current set of displayed URLs.

Fixes https://github.com/vector-im/riot-web/issues/10755

src/Terms.js

@@ -119,7 +119,8 @@ export async function startTermsFlow(
     if (unagreedPoliciesAndServicePairs.length > 0) {
         const newlyAgreedUrls = await interactionCallback(unagreedPoliciesAndServicePairs, [...agreedUrlSet]);
         console.log("User has agreed to URLs", newlyAgreedUrls);
-        agreedUrlSet = new Set(newlyAgreedUrls);
+        // Merge with previously agreed URLs
+        newlyAgreedUrls.forEach(url => agreedUrlSet.add(url));
     } else {
         console.log("User has already agreed to all required policies");
     }