test: fix typo

PR-URL: #39045
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>

test/common/README.md

@@ -932,8 +932,8 @@ functionality.
 * `dir` [<string>][] Directory to search for diagnostic report files.
 * return [<Array>][]
 
-Returns an array of diagnotic report file names found in `dir`. The files should
-have been generated by a process whose PID matches `pid`.
+Returns an array of diagnostic report file names found in `dir`. The files
+should have been generated by a process whose PID matches `pid`.
 
 ### `validate(filepath)`