test: add missing lifetime in recently added test.

Author: eddyb

src/test/compile-fail/where-equality-constraints.rs

@@ -10,7 +10,7 @@
 
 fn f() where u8 = u16 {}
 //~^ ERROR equality constraints are not yet supported in where clauses
-fn g() where for<'a> &(u8,) == u16, {}
+fn g() where for<'a> &'static (u8,) == u16, {}
 //~^ ERROR equality constraints are not yet supported in where clauses
 
 fn main() {}