Documentation: dev-tools: Fix typos in index.rst

Fixes a spelling error and removes an extra whitespace character.
Signed-off-by: Shreyans Devendra Doshi <0xinfosect0r@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/dev-tools/index.rst

@@ -4,7 +4,7 @@ Development tools for the kernel
 
 This document is a collection of documents about development tools that can
 be used to work on the kernel. For now, the documents have been pulled
-together without any significant effot to integrate them into a coherent
+together without any significant effort to integrate them into a coherent
 whole; patches welcome!
 
 .. class:: toc-title