MDL-85486 theme_boost: Fix single section page inplace editor

When course format is displayed as single section per page, the inplace editable
in the section page heading was incorrectly displaye, and the instructions panel
was not displayed.
Adding some specific styles to fix that behaviour.

public/theme/boost/scss/moodle/course.scss

@@ -667,8 +667,14 @@ $divider-hover-color: $primary !default;
     }
 }
 
-.single-section-page .header-action {
-    display: inline-block;
+.single-section-page {
+    .header-action {
+        display: inline-block;
+    }
+    // Revert page header styles to avoid conflict with inplace editable.
+    .page-context-header {
+        overflow: visible;
+    }
 }
 
 /* Default activity completion page */

public/theme/boost/style/moodle.css

@@ -30991,6 +30991,9 @@ table.calendartable caption {
 .single-section-page .header-action {
   display: inline-block;
 }
+.single-section-page .page-context-header {
+  overflow: visible;
+}
 
 /* Default activity completion page */
 .defaultactivitycompletion-item a {

public/theme/classic/style/moodle.css

@@ -30991,6 +30991,9 @@ table.calendartable caption {
 .single-section-page .header-action {
   display: inline-block;
 }
+.single-section-page .page-context-header {
+  overflow: visible;
+}
 
 /* Default activity completion page */
 .defaultactivitycompletion-item a {