buildkite pipeline: update container version to 5

Signed-off-by: Alexandra Iordache <aghecen@amazon.com>

Author: Alexandra Iordache

.buildkite/pipeline.yml

@@ -10,7 +10,7 @@ steps:
       platform: x86_64.metal
     plugins:
       - docker#v3.0.1:
-          image: "rustvmm/dev:v2"
+          image: "rustvmm/dev:v5"
           always-pull: true
 
   - label: "build-musl-x86-bzimage"
@@ -22,5 +22,5 @@ steps:
       platform: x86_64.metal
     plugins:
       - docker#v3.0.1:
-          image: "rustvmm/dev:v2"
+          image: "rustvmm/dev:v5"
           always-pull: true