Fixed case issue with 'fault-injection' in documentation

In the 'fault-injection' subdirectory, the first letter F
is capitalized, whereas in index.rst f is lowercase, but in
index.rst all other elements in the same column are capitalized.

Signed-off-by: "Ran.Park" <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Ran.Park

Documentation/fault-injection/index.rst

@@ -1,7 +1,7 @@
 .. SPDX-License-Identifier: GPL-2.0
 
 ===============
-fault-injection
+Fault-injection
 ===============
 
 .. toctree::