obsolete note about linked openssl

Although Qt 6 has ported to CMake build system, I can still see following configure note when I build Qt with linked openssl:

Note: When linking against OpenSSL, you can override the default library names through OPENSSL_LIBS. For example: OPENSSL_LIBS='-L/opt/ssl/lib -lssl -lcrypto' ./configure -openssl-linked

Apparently this note is obsolete. It seems that CMake build system does not use OPENSSL_LIBS variable. So this note should be removed, or be updated.

As a reference, if users want to override the default library names in CMake:

On MSVC, they should set these variables: SSL_EAY_DEBUG SSL_EAY_RELEASE LIB_EAY_DEBUG LIB_EAY_RELEASE.

On MinGW, they should set SSL_EAY and LIB_EAY variables.

On Other platforms, they should set OPENSSL_SSL_LIBRARY and OPENSSL_CRYPTO_LIBRARY variables. 

On MSVC, if users use openssl from http://slproweb.com/products/Win32OpenSSL.html, they may need to set OPENSSL_USE_STATIC_LIBS to TRUE to look for static libraries, and set OPENSSL_MSVC_STATIC_RT to TRUE to choose the MT version of the lib.