[8.x](backport #6064) [CI] Buildkite integration tests: Made AWS ARM …

…instance size equal to GCP x86_64 (#6067)

AWS ARM instance CPU and mem count equal to n1-standard-8 that we use on GCP

(cherry picked from commit be5debd)

(cherry picked from commit e8e4e7b)

---------

Co-authored-by: Pavel Zorin <pavel.zorin@elastic.co>
Co-authored-by: Olga Naidjonoka <olga_naidjonoka@epam.com>

.buildkite/bk.integration.pipeline.yml

@@ -91,7 +91,7 @@ steps:
         agents:
           provider: "aws"
           imagePrefix: "platform-ingest-beats-ubuntu-2404-aarch64"
-          instanceType: "m6g.xlarge"
+          instanceType: "m6g.2xlarge"
         matrix:
           - default
           - upgrade