Update protocol documentation (#1153)

See
[here](hazelcast/hazelcast-mono@77b1e0e#diff-37d9504ce60ecdf27711f36de75d440107d6ef841648903f4baf2df8344bac3aL56)
where default TLSv1.2 is changed.

And the current master has TLS
[here](https://github.com/hazelcast/hazelcast-mono/blob/9102331bb4025eb793f405aeaff05ae96c15edfd/hazelcast-enterprise/src/main/java/com/hazelcast/internal/nio/ssl/SSLEngineFactorySupport.java#L76)

Also SSL and TLSv1 and TLSv1.1 is old according to @kwart so I removed
them

docs/modules/security/pages/integrating-openssl.adoc

@@ -197,20 +197,15 @@ Available values are:
 ** `OPTIONAL` - server asks for a client certificate, but it doesn't
 require it
 * `ciphersuites`: Comma-separated list of cipher suite names allowed to be used.
-* `protocol`: Name of the algorithm which is used in your TLS/SSL. Its default
-value is `TLSv1.2`. Available values are:
-** `TLS`
-** `TLSv1`
-** `TLSv1.1`
+* `protocol`: Name of the algorithm which is used in your TLS. Its default
+value is empty, meaning the protocol version to use is not specified. Available
+values depend on the engine implementation but usually support:
+** `TLS` (equivalent to the empty value)
 ** `TLSv1.2`
-** `SSL` _(insecure!)_
-** `SSLv2` _(insecure!)_
-** `SSLv3` _(insecure!)_
+** `TLSv1.3`
 +
 For the
-`protocol` property, we recommend you to provide SSL or TLS with its version
-information, e.g., `TLSv1.2`. Note that if you
-provide only `SSL` or `TLS` as a value for the `protocol` property, they are
-converted to `SSLv3` and `TLSv1.2`, respectively. We strongly recommend to avoid
-SSL protocols.
+`protocol` property, we recommend you to provide TLS with its version
+information, e.g., `TLSv1.3`. It ensures the engine won't allow a fallback to an old, insecure version.
+
 * `validateIdentity`: Flag which allows enabling endpoint identity validation. It means, during the TLS handshake client verifies if the server's hostname (or IP address) matches the information in X.509 certificate (Subject Alternative Name extension). Possible values are `"true"` and `"false"` (default).