Move merge-section to `> .content` (#17582)

* Move `> .merge-section` to `> .content` scope

- Fixes a issue that started from
https://github.com/go-gitea/gitea/pull/17317
- Move `> .merge-section` to the `> .content` scope.
- Resolves #17480

* Move `.merge-section` back to outside scope

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

web_src/less/_repository.less

@@ -1018,7 +1018,7 @@
           }
         }
 
-        > .merge-section {
+        .merge-section {
           background-color: var(--color-box-body);
 
           .item {
@@ -1034,6 +1034,13 @@
             margin-bottom: -.25rem;
           }
 
+          @media @mediaSm {
+            .item-section {
+              align-items: flex-start;
+              flex-direction: column;
+            }
+          }
+
           .divider {
             margin-left: -1rem;
             margin-right: -1rem;
@@ -1046,6 +1053,7 @@
               border-right-color: var(--color-box-body);
             }
           }
+        }
 
         .markup {
           font-size: 14px;
@@ -1055,7 +1063,6 @@
           color: var(--color-text-light-2);
           font-style: italic;
         }
-        }
 
         .ui.form {
           .field {