piec: Add missing backslash to aws.md

JobBuild
13669
05-19 20:02
pull-kops-e2e-kubernetes-aws 1527413091128578048 1527379081400684544
pull-kops-verify-boilerplate 1527379081513930752
pull-kops-verify-generated 1527379081434238976
pull-kops-verify-gofmt 1527379081555873792
pull-kops-verify-golangci-lint 1527379081622982656
pull-kops-verify-gomod 1527379081480376320
pull-kops-verify-govet 1527379081589428224