ci: Align platforms for otel image with main repo

`nginx:otel` and friends are only built for amd64 and arm64/v8 right now:
- https://github.com/nginx/docker-nginx/blob/7f1d49f6f222f7e588a9066fd53a0ce43c3466a5/generate-stackbrew-library.sh#L103
- https://github.com/nginx/docker-nginx/blob/7f1d49f6f222f7e588a9066fd53a0ce43c3466a5/generate-stackbrew-library.sh#L139

Author: hangy

.github/workflows/alpine-mainline.yml

@@ -464,7 +464,7 @@ jobs:
         id: build
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
         with:
-          platforms: linux/amd64, linux/arm/v6, linux/arm/v7, linux/arm64, linux/386, linux/ppc64le, linux/riscv64, linux/s390x
+          platforms: linux/amd64, linux/arm64
           context: "{{ defaultContext }}:mainline/alpine-otel"
           labels: ${{ steps.meta.outputs.labels }}
           annotations: ${{ steps.meta.outputs.annotations }}

.github/workflows/alpine-stable.yml

@@ -435,7 +435,7 @@ jobs:
         id: build
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
         with:
-          platforms: linux/amd64, linux/arm/v6, linux/arm/v7, linux/arm64, linux/386, linux/ppc64le, linux/riscv64, linux/s390x
+          platforms: linux/amd64, linux/arm64
           context: "{{ defaultContext }}:stable/alpine-otel"
           labels: ${{ steps.meta.outputs.labels }}
           annotations: ${{ steps.meta.outputs.annotations }}

.github/workflows/debian-mainline.yml

@@ -348,8 +348,7 @@ jobs:
         id: build
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
         with:
-          platforms: linux/amd64, linux/arm/v7, linux/arm64, linux/386, linux/mips64le, linux/ppc64le, linux/s390x
-          # platforms: linux/amd64, linux/arm/v5, linux/arm/v7, linux/arm64, linux/386, linux/mips64le, linux/ppc64le, linux/s390x
+          platforms: linux/amd64, linux/arm64
           context: "{{ defaultContext }}:mainline/debian-otel"
           labels: ${{ steps.meta.outputs.labels }}
           annotations: ${{ steps.meta.outputs.annotations }}

.github/workflows/debian-stable.yml

@@ -328,8 +328,7 @@ jobs:
         id: build
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
         with:
-          platforms: linux/amd64, linux/arm/v7, linux/arm64, linux/386, linux/mips64le, linux/ppc64le, linux/s390x
-          # platforms: linux/amd64, linux/arm/v5, linux/arm/v7, linux/arm64, linux/386, linux/mips64le, linux/ppc64le, linux/s390x
+          platforms: linux/amd64, linux/arm64
           context: "{{ defaultContext }}:stable/debian-otel"
           labels: ${{ steps.meta.outputs.labels }}
           annotations: ${{ steps.meta.outputs.annotations }}