Merge pull request fluxcd#937 from fluxcd/add-release-label

Add 1.4.x release label

Author: matheuscscp

.github/labels.yaml

@@ -19,3 +19,6 @@
 - name: backport:release/v1.3.x
   description: To be backported to release/v1.3.x
   color: '#ffd700'
+- name: backport:release/v1.4.x
+  description: To be backported to release/v1.4.x
+  color: '#ffd700'