Remove course_id from answer model.

No migration added, per request from @edx/devops

OC-3033

problem_builder/models.py

@@ -39,15 +39,11 @@ class Answer(models.Model):
         # specify the app_label here.
         app_label = 'problem_builder'
         unique_together = (
-            ('student_id', 'course_id', 'name'),
             ('student_id', 'course_key', 'name'),
         )
 
     name = models.CharField(max_length=50, db_index=True)
     student_id = models.CharField(max_length=32, db_index=True)
-    # course_id is deprecated; it will be removed in next release.
-    course_id = models.CharField(max_length=50, db_index=True, blank=True, null=True, default=None)
-    # course_key is the new course_id replacement with extended max_length.
     course_key = models.CharField(max_length=255, db_index=True)
     student_input = models.TextField(blank=True, default='')
     created_on = models.DateTimeField('created on', auto_now_add=True)

setup.py

@@ -71,7 +71,7 @@ BLOCKS = [
 
 setup(
     name='xblock-problem-builder',
-    version='2.7.5',
+    version='2.7.6',
     description='XBlock - Problem Builder',
     packages=find_packages(),
     install_requires=[