syntax: back to -> for return type, no more =>

example/multiple_files/foo.zig

@@ -2,10 +2,10 @@ import "std.zig";
 
 // purposefully conflicting function with main.zig
 // but it's private so it should be OK
-fn private_function() => {
+fn private_function() {
     stdout.printf("OK 1\n");
 }
 
-pub fn print_text() => {
+pub fn print_text() {
     private_function();
 }