Remove single_precision_histogram for gpu_hist (#7828)

tests/python-gpu/test_gpu_basic_models.py

@@ -16,11 +16,11 @@ class TestGPUBasicModels:
     cpu_test_bm = test_bm.TestModels()
 
     def run_cls(self, X, y):
-        cls = xgb.XGBClassifier(tree_method='gpu_hist', single_precision_histogram=True)
+        cls = xgb.XGBClassifier(tree_method='gpu_hist')
         cls.fit(X, y)
         cls.get_booster().save_model('test_deterministic_gpu_hist-0.json')
 
-        cls = xgb.XGBClassifier(tree_method='gpu_hist', single_precision_histogram=True)
+        cls = xgb.XGBClassifier(tree_method='gpu_hist')
         cls.fit(X, y)
         cls.get_booster().save_model('test_deterministic_gpu_hist-1.json')
 

tests/python-gpu/test_gpu_updaters.py

@@ -15,7 +15,6 @@ parameter_strategy = strategies.fixed_dictionaries({
     'max_leaves': strategies.integers(0, 256),
     'max_bin': strategies.integers(2, 1024),
     'grow_policy': strategies.sampled_from(['lossguide', 'depthwise']),
-    'single_precision_histogram': strategies.booleans(),
     'min_child_weight': strategies.floats(0.5, 2.0),
     'seed': strategies.integers(0, 10),
     # We cannot enable subsampling as the training loss can increase