Update README.md (#36)

Fix copy-paste error on `singletons.ERC1820Registry` in README

README.md

@@ -217,7 +217,7 @@ Only accepts failures due to the transaction running out of gas.
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 ### singletons
-#### async time.ERC1820Registry (funder)
+#### async singletons.ERC1820Registry (funder)
 Returns an instance of an [ERC1820Registry](https://eips.ethereum.org/EIPS/eip-1820) deployed as per the specification (i.e. the registry is located at the canonical address). This can be called multiple times to retrieve the same instance.
 
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