bin/update-schedule.py: Fix the fallback to the current year

Looks like I forgot to test that path. This fixes the following error:
```
    wd = os.path.join(basedir, year)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen posixpath>", line 90, in join
  File "<frozen genericpath>", line 152, in _check_arg_types
TypeError: join() argument must be str, bytes, or os.PathLike object, not 'int'
```

bin/update-schedule.py

@@ -10,7 +10,7 @@
 def select_year():
     """Select the year, cd into the corresponding directory, and return the year."""
     # Default to the current year:
-    year = int(datetime.now().year)
+    year = str(datetime.now().year)
 
     # Override based on the current directory:
     dirname = os.getcwd().split('/')[-1]