Merge pull request #1990 from fluxcd/label-1.8

Add backport:release/v1.8.x label

Author: matheuscscp

.github/labels.yaml

@@ -40,3 +40,6 @@
 - name: backport:release/v1.7.x
   description: To be backported to release/v1.7.x
   color: '#ffd700'
+- name: backport:release/v1.8.x
+  description: To be backported to release/v1.8.x
+  color: '#ffd700'