Move when statement to block

The when statement is supposed to be on the block, not on the individual task.

It affects all tasks within the block (they're all to be executed when ma1sd is enabled and self-building is requested0.

roles/matrix-ma1sd/tasks/setup_ma1sd.yml

@@ -61,7 +61,6 @@
     shell: "./gradlew dockerBuild"
     args:
       chdir: "{{ matrix_ma1sd_docker_src_files_path }}"
-    when: "matrix_ma1sd_enabled|bool and matrix_ma1sd_container_image_self_build"
 
   - name: Ensure ma1sd Docker image is tagged correctly
     docker_image:
@@ -69,7 +68,7 @@
       repository: "{{ matrix_ma1sd_docker_image }}"
       force_tag: yes
       source: local
-    when: "matrix_ma1sd_enabled|bool and matrix_ma1sd_container_image_self_build"
+  when: "matrix_ma1sd_enabled|bool and matrix_ma1sd_container_image_self_build"
 
 - name: Ensure ma1sd config installed
   copy: