Remove key from `addPanel` as it is not a valid prop

[DrJacobHolden]

Hi! 👋

Firstly, thanks for your work on this project! 🙂

Today I used patch-package to patch @storybook/addon-knobs@7.0.2.

Specifically - there is an error displaying in the console every time I open a Story which says that key is not a prop. The same issue was fixed for addon-designs in this PR.

Here is the diff that solved my problem:

diff --git a/node_modules/@storybook/addon-knobs/dist/register.js b/node_modules/@storybook/addon-knobs/dist/register.js
index 2a88bf1..f4ef372 100644
--- a/node_modules/@storybook/addon-knobs/dist/register.js
+++ b/node_modules/@storybook/addon-knobs/dist/register.js
@@ -13,11 +13,9 @@ _addons.addons.register(_shared.ADDON_ID, function (api) {
   _addons.addons.addPanel(_shared.PANEL_ID, {
     title: (0, _title.createTitleListener)(api),
     render: function render(_ref) {
-      var active = _ref.active,
-        key = _ref.key;
+      var active = _ref.active;
       return /*#__PURE__*/React.createElement(_Panel["default"], {
         api: api,
-        key: key,
         active: active
       });
     },

This issue body was partially generated by patch-package.