drop missing flag from vmalert (#3991)

Author: idoqo

managed/services/supervisord/supervisord.go

@@ -524,7 +524,6 @@ command =
 		--external.url={{ .VMURL }}
 		--datasource.url={{ .VMURL }}
 		--remoteRead.url={{ .VMURL }}
-		--remoteRead.ignoreRestoreErrors=false
 		--remoteWrite.url={{ .VMURL }}
 		--rule=/srv/prometheus/rules/*.yml
 		--httpListenAddr={{ .InterfaceToBind }}:8880