Fix wrong examples in assessor docs (#5520)

docs/source/hpo/assessors.rst

@@ -26,7 +26,7 @@ To use a built-in assessor you need to specify its name and arguments:
 .. code-block:: python
 
     config.assessor.name = 'Medianstop'
-    config.tuner.class_args = {'optimize_mode': 'maximize'}
+    config.assessor.class_args = {'optimize_mode': 'maximize'}
 
 Built-in Assessors
 ------------------

nni/algorithms/hpo/curvefitting_assessor/curvefitting_assessor.py

@@ -40,7 +40,7 @@ class CurvefittingAssessor(Assessor):
     .. code-block::
 
         config.assessor.name = 'Curvefitting'
-        config.tuner.class_args = {
+        config.assessor.class_args = {
             'epoch_num': 20,
             'start_step': 6,
             'threshold': 9,

nni/algorithms/hpo/medianstop_assessor.py

@@ -36,7 +36,7 @@ class MedianstopAssessor(Assessor):
     .. code-block::
 
         config.assessor.name = 'Medianstop'
-        config.tuner.class_args = {
+        config.assessor.class_args = {
             'optimize_mode': 'maximize',
             'start_step': 5
         }