[python] drop unnecessary dependency to pycrypto

PR project-chip#21567 introduced an unnecessary dependency to pycrypto. From PyPI it
seems that pycrypto is largely unmaintained, and I did not found a use
in the Python bindings or in the Python test.

Also drop the comment about cryptography and ecdsa usage as the library
is meanwhile used in the core CHIP Python libraries.

src/controller/python/BUILD.gn

@@ -309,10 +309,7 @@ chip_python_wheel_action("chip-core") {
     "ipdb",
     "deprecation",
     "mobly",
-
-    # Crypto libraries for complex tests and internal Python controller usage
     "cryptography",
-    "pycrypto",
     "ecdsa",
   ]