Add 1.5.x release label

Signed-off-by: Matheus Pimenta <[email protected]>

Author: matheuscscp

.github/labels.yaml

@@ -31,3 +31,6 @@
 - name: backport:release/v1.4.x
   description: To be backported to release/v1.4.x
   color: '#ffd700'
+- name: backport:release/v1.5.x
+  description: To be backported to release/v1.5.x
+  color: '#ffd700'