refactor: Add thread safety annotation to `BanMan::SweepBanned()`

src/banman.cpp

@@ -179,10 +179,11 @@ void BanMan::GetBanned(banmap_t& banmap)
 
 void BanMan::SweepBanned()
 {
+    AssertLockHeld(m_cs_banned);
+
     int64_t now = GetTime();
     bool notify_ui = false;
     {
-        LOCK(m_cs_banned);
         banmap_t::iterator it = m_banned.begin();
         while (it != m_banned.end()) {
             CSubNet sub_net = (*it).first;

src/banman.h

@@ -85,7 +85,7 @@ private:
     //!set the "dirty" flag for the banlist
     void SetBannedSetDirty(bool dirty = true);
     //!clean unused entries (if bantime has expired)
-    void SweepBanned();
+    void SweepBanned() EXCLUSIVE_LOCKS_REQUIRED(m_cs_banned);
 
     RecursiveMutex m_cs_banned;
     banmap_t m_banned GUARDED_BY(m_cs_banned);