Remove tools and bots section.

There's almost no information in there. We can add it back when we have
anything useful to say.

Author: m-ou-se

src/SUMMARY.md

@@ -51,10 +51,3 @@
     - [safety comments policy](./documentation/safety-comments.md)
     - [how to write documentation](./documentation/how-to-write-documentation.md)
     - [reviewing doc changes](./documentation/reviewing-doc-changes.md)
-
----
-
-- [Tools and bots](./tools-and-bots/summary.md)
-    - [`@bors`](./tools-and-bots/bors.md)
-    - [`@rust-timer`](./tools-and-bots/timer.md)
-    - [`@craterbot`](./tools-and-bots/crater.md)