Merge #16960: doc: replace outdated OpenSSL comment in test README

27fcb40 doc: replace outdated OpenSSL comment in test README (fanquake)

Pull request description:

  The OpenSSL dependency was removed in #15826.

ACKs for top commit:
  laanwj:
    ACK 27fcb40
  theStack:
    ACK bitcoin/bitcoin@27fcb40

Tree-SHA512: eb7a3b18fefa91e6f27c50fa065d6cc330f7b633ae8ee51145cdeec4df51dea5155f0d1fa91e75f1202adef04e063f3eda12773cd00a093f29f5a5e83c4fda73

Author: laanwj

test/functional/README.md

@@ -116,7 +116,7 @@ Basic code to support P2P connectivity to a bitcoind.
 Utilities for manipulating transaction scripts (originally from python-bitcoinlib)
 
 #### [test_framework/key.py](test_framework/key.py)
-Wrapper around OpenSSL EC_Key (originally from python-bitcoinlib)
+Test-only secp256k1 elliptic curve implementation
 
 #### [test_framework/bignum.py](test_framework/bignum.py)
 Helpers for script.py