Upgrade py-trie to v2-alpha.3

Specifically need to fix the typing-extensions conflict resolved here:
ethereum/py-trie#117

Author: carver

newsfragments/1953.misc.rst

@@ -0,0 +1 @@
+Upgrade py-trie to v2.0.0-alpha.3

setup.py

@@ -16,7 +16,7 @@
         "py-ecc>=1.4.7,<5.0.0",
         "pyethash>=0.1.27,<1.0.0",
         "rlp>=1.1.0,<2.0.0",
-        "trie==2.0.0-alpha.2",
+        "trie==2.0.0-alpha.3",
     ],
     # The eth-extra sections is for libraries that the evm does not
     # explicitly need to function and hence should not depend on.