CI: change armvirt reference to armsr

The armvirt target has been renamed to armsr.

Signed-off-by: Mathew McBride <[email protected]>

.github/labeler.yml

@@ -5,8 +5,8 @@
   - "target/linux/apm821xx/**"
 "target/archs38":
   - "target/linux/archs38/**"
-"target/armvirt":
-  - "target/linux/armvirt/**"
+"target/armsr":
+  - "target/linux/armsr/**"
 "target/at91":
   - "target/linux/at91/**"
   - "package/boot/at91bootstrap/**"