fix the docker link in the ISSUE_TEMPLATE

Signed-off-by: Yury Vidineev <adeptg@gmail.com>

.github/ISSUE_TEMPLATE.md

@@ -6,7 +6,7 @@
 	Before filing a bug report, note that running node_exporter in Docker is
 	not recommended, for the reasons detailed in the README:
 
-	https://github.com/prometheus/node_exporter#using-docker
+	https://github.com/prometheus/node_exporter#docker
 
 	Finally, also note that node_exporter is focused on *NIX kernels, and the
 	WMI exporter should be used instead on Windows.