test: update cases to silence 'var is never mutated' errors

test/cases/enum_values.1.zig

@@ -2,7 +2,9 @@ const Number = enum { One, Two, Three };
 
 pub fn main() void {
     var number1 = Number.One;
+    _ = &number1;
     var number2: Number = .Two;
+    _ = &number2;
     const number3: Number = @enumFromInt(2);
     assert(number1 != number2);
     assert(number2 != number3);
@@ -10,6 +12,7 @@ pub fn main() void {
     assert(@intFromEnum(number2) == 1);
     assert(@intFromEnum(number3) == 2);
     var x: Number = .Two;
+    _ = &x;
     assert(number2 == x);
 
     return;