docs: Remove conflicting /start/ redirect

Follows-up 3332800, in which I mistakenly copied the
`redirect_from: /start/` in /QUnit/load.md from /QUnit/start.md when
I copied something else.

Fortunately, Jekyll parsed the files in the order such that the
original one "won" so no traffic was actually diverted.

Unfortunately, there is no build time error or warning about such
conflicts. Ref jekyll/jekyll-redirect-from#266

docs/QUnit/load.md

@@ -4,8 +4,6 @@ title: QUnit.load()
 excerpt: Inform the test runner that code has finished loading.
 groups:
   - deprecated
-redirect_from:
-  - "/start/"
 version_added: "1.0.0"
 version_deprecated: "unreleased"
 ---