Remove the show property from the modal plugin (#32279)

Drop the support of show property from the modal plugin.
When creating the new modal instance in v5, the `show` property does not work anymore, so instead of fixing the behavior just removing it permanently to keep the consistency between all the plugins. (All other plugins require the `show()` method to be called on the instances to be shown)

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

js/src/modal.js

@@ -37,15 +37,13 @@ const ESCAPE_KEY = 'Escape'
 const Default = {
   backdrop: true,
   keyboard: true,
-  focus: true,
-  show: true
+  focus: true
 }
 
 const DefaultType = {
   backdrop: '(boolean|string)',
   keyboard: 'boolean',
-  focus: 'boolean',
-  show: 'boolean'
+  focus: 'boolean'
 }
 
 const EVENT_HIDE = `hide${EVENT_KEY}`
@@ -557,8 +555,6 @@ class Modal extends BaseComponent {
         }
 
         data[config](relatedTarget)
-      } else if (_config.show) {
-        data.show(relatedTarget)
       }
     })
   }