[ci] upgrade aarch64 ec2 instance

Author: kateinoigakukun

.github/workflows/build-toolchain.yml

@@ -41,7 +41,7 @@ jobs:
           mode: start
           github-token: ${{ secrets.SWIFTWASM_BUILDBOT_TOKEN }}
           ec2-image-id: ami-03803f6b50b56647a # swiftwasm-ci/ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-arm64-server-20221201
-          ec2-instance-type: c6g.large
+          ec2-instance-type: c6g.xlarge
           subnet-id: subnet-327f4a13
           security-group-id: sg-0429f5ec2bee9dc0c
   stop-runner: