chore: remove QEMU setup step from multi-arch build workflow and update README to reflect changes

Author: Yukaii

.github/workflows/build-multi-arch-native.yml

@@ -49,9 +49,6 @@ jobs:
           images: hackmdio/${{ inputs.image_name }}
           tags: |
             type=raw,value=${{ inputs.tag_prefix }}-{{sha}}
-      -
-        name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
       -
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3

README.md

@@ -20,8 +20,6 @@ Example parameters:
 
 **Prerequisites**: Set up `DOCKERHUB_USERNAME` and `DOCKERHUB_TOKEN` secrets in your GitHub repository.
 
-**Note**: The workflow currently uses QEMU emulation on ubuntu-latest runners. For true native builds, change the ARM64 runner to `ubuntu-latest-arm64` if available in your GitHub account.
-
 ### Manual Native Build Process
 
 ```bash