Add backport label for Flux 2.7

Signed-off-by: Matheus Pimenta <matheuscscp@gmail.com>

.github/labels.yaml

@@ -44,12 +44,12 @@
   description: Feature request proposals in the RFC format
   color: '#D621C3'
   aliases: ['area/RFC']
-- name: backport:release/v2.4.x
-  description: To be backported to release/v2.4.x
-  color: '#ffd700'
 - name: backport:release/v2.5.x
   description: To be backported to release/v2.5.x
   color: '#ffd700'
 - name: backport:release/v2.6.x
   description: To be backported to release/v2.6.x
   color: '#ffd700'
+- name: backport:release/v2.7.x
+  description: To be backported to release/v2.7.x
+  color: '#ffd700'