_content/doc: fix a small typo

it's --> its

Change-Id: Ia3d64b636704ce0108161c3c194233258c4b3d06
Reviewed-on: https://go-review.googlesource.com/c/website/+/377194
Reviewed-by: Russ Cox <[email protected]>
Run-TryBot: Emmanuel Odeke <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: DO NOT USE <[email protected]>

Author: eliben

_content/doc/fuzz/index.md

@@ -25,7 +25,7 @@ through the code being fuzzed to find and report failures to the user. Since it
 can reach edge cases which humans often miss, fuzz testing can be particularly
 valuable for finding security exploits and vulnerabilities.
 
-Below is an example of a [fuzz test](#glos-fuzz-test), highlighting it's main
+Below is an example of a [fuzz test](#glos-fuzz-test), highlighting its main
 components.
 
 <img alt="Example code showing the overall fuzz test, with a fuzz target within