Fix some typos (GH-14435)

diff --git a/Modules/_abc.c b/Modules/_abc.c
index 7233690..219ea0d 100644
--- a/Modules/_abc.c
+++ b/Modules/_abc.c
@@ -554,7 +554,7 @@
 }
 
 
-// Return -1 when exception occured.
+// Return -1 when exception occurred.
 // Return 1 when result is set.
 // Return 0 otherwise.
 static int subclasscheck_check_registry(_abc_data *impl, PyObject *subclass,
@@ -666,7 +666,7 @@
 
     /* 5. Check if it's a subclass of a registered class (recursive). */
     if (subclasscheck_check_registry(impl, subclass, &result)) {
-        // Exception occured or result is set.
+        // Exception occurred or result is set.
         goto end;
     }