CLEANUP: Fix a typo in the checks header file

Fixes a typo in the code comments of the checks header file.
diff --git a/include/types/checks.h b/include/types/checks.h
index e0a4bd6..364eee8 100644
--- a/include/types/checks.h
+++ b/include/types/checks.h
@@ -224,7 +224,7 @@
 	/* match type uses NON-NULL pointer from either string or expect_regex below */
 	/* sent string is string */
 	char *string;                           /* sent or expected string */
-	int string_len;                         /* string lenght */
+	int string_len;                         /* string length */
 	struct my_regex *expect_regex;          /* expected */
 	int inverse;                            /* 0 = regular match, 1 = inverse match */
 	unsigned short port;                    /* port to connect to */