doc: do not reference SSL when discussing SNI

Co-authored-by: Rich Trott <rtrott@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/41549
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/tls.md

@@ -115,7 +115,7 @@ SNI (Server Name Indication) are TLS handshake extensions:
 
 * ALPN: Allows the use of one TLS server for multiple protocols (HTTP, HTTP/2)
 * SNI: Allows the use of one TLS server for multiple hostnames with different
-  SSL certificates.
+  certificates.
 
 ### Pre-shared keys