UPSTREAM: <squash>: bump build image and more memory

Signed-off-by: Dr. Stefan Schimanski <[email protected]>

Author: sttts

.prow.yaml

@@ -7,7 +7,7 @@ presubmits:
       preset-goproxy: "true"
     spec:
       containers:
-        - image: ghcr.io/kcp-dev/infra/build:1.20.9-1
-          command:
-            - make
-            - test
+      - image: ghcr.io/kcp-dev/infra/build:1.21.8-1
+        command:
+        - make
+        - test