mediaapi/types: Rename member to ActiveRemoteRequests.MXCToCond

Clearer that it's a map from mxc URLs to sync.Cond

src/github.com/matrix-org/dendrite/mediaapi/routing/routing.go

@@ -40,7 +40,7 @@ func Setup(servMux *http.ServeMux, httpClient *http.Client, cfg *config.MediaAPI
 	}))
 
 	activeRemoteRequests := &types.ActiveRemoteRequests{
-		Set: map[string]*sync.Cond{},
+		MXCToCond: map[string]*sync.Cond{},
 	}
 	r0mux.Handle("/download/{serverName}/{mediaId}",
 		prometheus.InstrumentHandler("download", http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {

src/github.com/matrix-org/dendrite/mediaapi/types/types.go

@@ -68,5 +68,5 @@ type MediaMetadata struct {
 type ActiveRemoteRequests struct {
 	sync.Mutex
 	// The string key is an mxc:// URL
-	Set map[string]*sync.Cond
+	MXCToCond map[string]*sync.Cond
 }