Correct Go version when running the coverage report (#5476) (#5478)

Signed-off-by: Alexandros Sapranidis <alexandros@elastic.co>
(cherry picked from commit a11954b)

Co-authored-by: Alexandros Sapranidis <alexandros@elastic.co>

Author: mergify[bot]

.buildkite/pipeline.yml

@@ -171,7 +171,7 @@ steps:
     artifact_paths:
       - "build/TEST-go-unit.cov"
     agents:
-      image: "golang:1.20.10"
+      image: "golang:1.22.6"
     depends_on:
       - unit-tests
       - extended-windows