ssl: fix test_tmp_dh and test_tmp_dh_callback with OpenSSL 4.0

OpenSSL master added support for RFC 7919 groups in TLS 1.2. They are
preferred over SSLContext#tmp_dh= or #tmp_dh_callback= values if the
client advertises them in the supported_groups extension.

Author: rhenium

test/openssl/test_ssl.rb

@@ -1909,7 +1909,9 @@ def test_tmp_dh_callback
       }
     }
     start_server(ctx_proc: ctx_proc) do |port|
-      server_connect(port) { |ssl|
+      ctx = OpenSSL::SSL::SSLContext.new
+      ctx.groups = "P-256" # Exclude RFC 7919 groups
+      server_connect(port, ctx) { |ssl|
         assert called, "dh callback should be called"
         assert_equal dh.to_der, ssl.tmp_key.to_der
       }
@@ -2172,7 +2174,9 @@ def test_tmp_dh
       ctx.tmp_dh = dh
     }
     start_server(ctx_proc: ctx_proc) do |port|
-      server_connect(port) { |ssl|
+      ctx = OpenSSL::SSL::SSLContext.new
+      ctx.groups = "P-256" # Exclude RFC 7919 groups
+      server_connect(port, ctx) { |ssl|
         assert_equal dh.to_der, ssl.tmp_key.to_der
       }
     end