python{26,3[2-6]}: use supported_archs to exclude arm64

lang/python35/Portfile

@@ -68,16 +68,8 @@ openssl.branch      1.1
 configure.cppflags-prepend  -I[openssl::include_dir]
 configure.ldflags-prepend   -L[openssl::lib_dir]
 
-platform darwin arm {
-    known_fail  yes
-    if {$build_arch ne "x86_64"} {
-        pre-fetch {
-            error "${name} cannot be built for Apple Silicon"
-        }
-        depends_build
-        depends_lib
-        depends_run
-    }
+if {${os.platform} eq "darwin" && ${os.major} >= 20} {
+    supported_archs x86_64
 }
 
 # blacklist llvm-gcc-4.2 compiler known to produce bad code