CONTRIBUTING.md: Fix typo (pytorch#11022)

### Summary
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Requests](https://github.com/pytorch/executorch/blob/main/CONTRIBUTING.md#pull-requests)
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### Test plan
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Author: psiddh

CONTRIBUTING.md

@@ -420,7 +420,7 @@ for basics.
 - Use [this](docs/source/backend-delegates-integration.md) guide when
   integrating your delegate with ExecuTorch.
 - Refer to [this](docs/source/backend-delegates-dependencies.md) set of
-  guidelines when including a third-party depenency for your delegate.
+  guidelines when including a third-party dependency for your delegate.