Fix a typo and remove an old file

Author: SimGus

syntax-specs.md

@@ -343,7 +343,7 @@ If we wanted to have `astronaut` as the entity value for all those strings, we w
     ~[astronaut] = astronaut
     // other rules
 ```
-Here all strings generated by the rule (whatever the number of tokens in the rule) will take `astronaut` as entity value. Of course, any value can be put after the equal sign `≃`.
+Here all strings generated by the rule (whatever the number of tokens in the rule) will take `astronaut` as entity value. Of course, any value can be put after the equal sign `=`.
 
 The other way to do this is the following:
 ```