Bump version of Python server (#4062)

The Python server version must be semver compatible with the Rust server
version it's binding to. The version mismatch between these servers
causes dependency conflicts, as shown by the multiple versions being
pulled in:
```
aws-smithy-http-server v0.63.3
└── aws-smithy-http-server-python v0.63.2
    └── amzn-pokemon-service-python-server-sdk v0.1.0

aws-smithy-http-server v0.64.0
└── amzn-pokemon-service-python-server-sdk v0.1.0
```

This leads to type incompatibility errors in the server bindings.

Co-authored-by: Fahad Zubair <fahadzub@amazon.com>

Author: drganjoo

rust-runtime/aws-smithy-http-server-python/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aws-smithy-http-server-python"
-version = "0.63.3"
+version = "0.64.0"
 authors = ["Smithy Rust Server <smithy-rs-server@amazon.com>"]
 edition = "2021"
 license = "Apache-2.0"