Fix typo.

biscuit/apps/alsijil/models.py

@@ -23,7 +23,7 @@ class PersonalNote(SchoolRelated):
 
 class LessonDocumentation(SchoolRelated):
     week = models.IntegerField()
-    lesson_period = models.ForeigbKey('chronos.LessonPeriod', models.CASCADE)
+    lesson_period = models.ForeignKey('chronos.LessonPeriod', models.CASCADE)
 
     topic = models.CharField(verbose_name=_('Lesson topic'), max_length=200, blank=True)
     homework = models.CharField(verbose_name=_('Homework'), max_length=200, blank=True)