fix wording

Author: timfel

docs/contributor/IMPLEMENTATION_DETAILS.md

@@ -261,13 +261,13 @@ many C extensions are not written to reentrant.
 So, commonly at any given time there is only one Graal Python thread executing
 and all the other threads are waiting to acquire the GIL. If the Python
 interpreter shuts down, there are two sets of threads we need to deal with:
-"well-behaved" threads created using the `threading` are interrupted and joined
-using the `threading` module's `shutdown` function. Daemon threads or threads
-created using the internal Python `_thread` module cannot be joined in this
-way. For those threads, we invalidate their `PythonThreadState` (a thread-local
-data structure) and use the Java `Thread#interrupt` method to interrupt their
-waiting on the GIL. This exception is handled by checking if the thread state
-has been invalidated and if so, just exit the thread gracefully.
+"well-behaved" threads created using the `threading` module are interrupted and
+joined using the `threading` module's `shutdown` function. Daemon threads or
+threads created using the internal Python `_thread` module cannot be joined in
+this way. For those threads, we invalidate their `PythonThreadState` (a
+thread-local data structure) and use the Java `Thread#interrupt` method to
+interrupt their waiting on the GIL. This exception is handled by checking if the
+thread state has been invalidated and if so, just exit the thread gracefully.
 
 For embedders, it may be important to be able to interrupt Python threads by
 other means. We use the TruffleSafepoint mechanism to mark our threads waiting