update discover coverage

Author: zou3519

test/discover_coverage.py

@@ -727,6 +727,7 @@ def supports_jvpvjp(self):
         exemptions = {
             # we have support (see OpInfo), testing artifact
             'nn.functional.dropout2d',
+            'nn.functional.dropout',
             # exception: we dont even support double backward for this
             'nn.functional.hardswish',
             'bernoulli',  # this isn't differentiable