Fix POSIX shell compatibility in check-versions task

Use POSIX-compatible `[ ]` and `=` instead of bash-specific `[[ ]]`
and `==` to ensure the task works in environments where the default
shell is sh rather than bash.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dahlia

.github/workflows/main.yaml

@@ -241,7 +241,7 @@ jobs:
         echo version="$(jq -r .version deno.json)" >> $GITHUB_OUTPUT
         echo short_version="$(jq -r .version deno.json | sed 's/[+].*//')" >> $GITHUB_OUTPUT
       working-directory: ${{ github.workspace }}/packages/fedify/
-    - run: mise run check-versions -- --fix
+    - run: mise run check-versions --fix
     - if: github.ref_type == 'tag'
       run: |
         set -ex

mise.toml

@@ -28,7 +28,7 @@ run = "deno fmt --check && deno lint && deno check --unstable-temporal $(deno ev
 description = "Check that all package versions are consistent across the monorepo"
 usage = 'flag "--fix" help="Automatically fix version mismatches"'
 run = '''
-if [[ "${usage_fix}" == "true" ]]; then
+if [ "${usage_fix}" = "true" ]; then
   deno run --allow-read --allow-write scripts/check_versions.ts --fix
 else
   deno task check-versions