Remove mipsle from Docker build matrix

No base Docker image (Alpine, Debian, etc.) supports mipsle.

Author: nekohasekai

.github/workflows/docker.yml

@@ -166,7 +166,7 @@ jobs:
           - { platform: "linux/arm/v7" }
           - { platform: "linux/arm64" }
           - { platform: "linux/386" }
-          - { platform: "linux/mipsle", base_image: "debian:stable-slim" }
+          # mipsle: no base Docker image available for this platform
           - { platform: "linux/ppc64le" }
           - { platform: "linux/riscv64" }
           - { platform: "linux/s390x" }