Use unique_lock when loading 7TV badges (#4402)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/providers/seventv/SeventvBadges.cpp

@@ -45,7 +45,7 @@ void SeventvBadges::loadSeventvBadges()
         .onSuccess([this](const NetworkResult &result) -> Outcome {
             auto root = result.parseJson();
 
-            std::shared_lock lock(this->mutex_);
+            std::unique_lock lock(this->mutex_);
 
             int index = 0;
             for (const auto &jsonBadge : root.value("badges").toArray())