Replace minmax with setting min-width

- This addresses [this issue][1].
- `minmax` is set at the parent level which we were
only applying sometimes and is easy to overlook. It
seemed that we were coupling the parents to knowing
about certain children contents. What if we just set
the problematic child's `min-width`?

[1]: https://gitlab.com/gitlab-org/gitlab/-/issues/296222

app/assets/stylesheets/framework/diffs.scss

@@ -588,6 +588,12 @@ table.code {
 
 // Merge request diff grid layout
 .diff-grid {
+  .diff-td {
+    // By default min-width is auto with 1fr which causes some overflow problems
+    // https://gitlab.com/gitlab-org/gitlab/-/issues/296222
+    min-width: 0;
+  }
+
   .diff-grid-row {
     display: grid;
     grid-template-columns: 1fr 1fr;
@@ -601,27 +607,27 @@ table.code {
 
   .diff-grid-comments {
     display: grid;
-    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
+    grid-template-columns: 1fr 1fr;
   }
 
   .diff-grid-drafts {
     display: grid;
-    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
+    grid-template-columns: 1fr 1fr;
   }
 
   &.inline {
     .diff-grid-comments {
       display: grid;
-      grid-template-columns: minmax(0, 1fr);
+      grid-template-columns: 1fr;
     }
 
     .diff-grid-drafts {
       display: grid;
-      grid-template-columns: minmax(0, 1fr);
+      grid-template-columns: 1fr;
     }
 
     .diff-grid-row {
-      grid-template-columns: minmax(0, 1fr);
+      grid-template-columns: 1fr;
     }
 
     .diff-grid-left,