ci: add seccomp 2.5.6 and 2.6.0

Those were released last week:
 - https://github.com/seccomp/libseccomp/releases/tag/v2.5.6
 - https://github.com/seccomp/libseccomp/releases/tag/v2.6.0

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

.github/workflows/test.yml

@@ -16,7 +16,7 @@ jobs:
       fail-fast: false
       matrix:
         go-version: [1.22.x, 1.23.x]
-        libseccomp: ["v2.3.3", "v2.4.4", "v2.5.5", "HEAD"]
+        libseccomp: ["v2.3.3", "v2.4.4", "v2.5.6", "v2.6.0", "HEAD"]
 
     steps: