Revert "Test pre- and postfix autoincrement on Num"

This reverts commit c8889fc.

Turns out those ops were already covered in commit
2a3cdb2 / file S02-types/num.t

S03-operators/autoincrement.t

@@ -4,7 +4,7 @@ use Test;
 # Tests for auto-increment and auto-decrement operators
 # originally from Perl 5, by way of t/operators/auto.t
 
-plan 88;
+plan 80;
 
 #L<S03/Autoincrement precedence>
 
@@ -48,19 +48,6 @@ is(0 + ++%z{0} - 1, $base, '0 + ++%z{0} - 1');
 is(0 + --%z{0} + 0, $base, '0 + --%z{0} + 0');
 is(%z{0},           $base, '%z{0}');
 
-# Incrementing and decrementing Num
-{
-    my Num $x = 42e0;
-    is $x++, 42e0, 'result of Num++';
-    is $x,   43e0, 'side effect of Num++';
-    is $x--, 43e0, 'result of Num--';
-    is $x,   42e0, 'side effect of Num+--';
-    is ++$x, 43e0, 'result of ++Num';
-    is $x,   43e0, 'side effect of ++Num';
-    is --$x, 42e0, 'result of --Num';
-    is $x,   42e0, 'side effect of --Num';
-}
-
 # Increment of a Str
 #L<S03/Autoincrement precedence/Increment of a>