Removed description of no longer used ssl_single_dh_use.

docs/UserManual.md

@@ -429,11 +429,6 @@ TLS1.0+TLS1.1+TLS1.2 | 2
 TLS1.1+TLS1.2 | 3
 TLS1.2 | 4
 
-### ssl_single_dh_use `no`
-Enables creating new DH key during every negotiation. This delays
-creation of DH key until connection is negotiated instead of
-creating DH key only once during initialization.
-
 # Lua Scripts and Lua Server Pages
 Pre-built Windows and Mac civetweb binaries have built-in Lua scripting
 support as well as support for Lua Server Pages.