fix build with OTP >= 20.1 on macos

we didn't match the regexp on this platform. this change fixed it.
inspired by change from @g-andrade

Author: benoitc

rebar.config

@@ -5,7 +5,7 @@
             {platform_define, "R14", no_callback_support},
             {platform_define, "^[0-9]+", namespaced_types},
             {platform_define, "^R", no_proxy_sni_support},
-            {platform_define, "^(19)|(20)", no_customize_hostname_check},
+            {platform_define, "^(19|(20))", no_customize_hostname_check},
             {platform_define, "^20\.3", buggy_chacha_ciphers}
            ]}.