(core) Fix scrollbar in code view

Summary:
The scrollbar wasn't properly positioned inside the
bounds of the main panel.

Test Plan: Manual.

Reviewers: jarek

Reviewed By: jarek

Subscribers: paulfitz, jarek

Differential Revision: https://phab.getgrist.com/D4357

app/client/components/CodeEditorPanel.css

@@ -1,8 +1,5 @@
 .g-code-panel {
-  position:absolute;
-  width: 100%;
-  height: 100%;
-  margin: 10px;
+  padding: 10px;
   overflow: auto;
 }
 

app/client/components/GristDoc.ts

@@ -655,15 +655,10 @@ export class GristDoc extends DisposableWithEvents {
    * Builds the DOM for this GristDoc.
    */
   public buildDom() {
-    const isMaximized = Computed.create(this, use => use(this.maximizedSectionId) !== null);
-    const isPopup = Computed.create(this, use => {
-      return ['data', 'settings'].includes(use(this.activeViewId) as any) // On Raw data or doc settings pages
-        || use(isMaximized) // Layout has a maximized section visible
-        || Boolean(use(this._popupSectionOptions)); // Layout has a popup section visible
-    });
     return cssViewContentPane(
       testId('gristdoc'),
-      cssViewContentPane.cls("-contents", isPopup),
+      cssViewContentPane.cls("-special-page", use =>
+        ['data', 'settings', 'code'].includes(use(this.activeViewId) as string)),
       dom.maybe(this._isRickRowing, () => cssStopRickRowingButton(
         cssCloseIcon('CrossBig'),
         dom.on('click', () => {
@@ -2052,8 +2047,9 @@ const cssViewContentPane = styled('div', `
       padding: 0px;
     }
   }
-  &-contents {
+  &-special-page {
     overflow: hidden;
+    padding: 0px;
   }
 `);