Remove implementation notes obsoleted by 2015.09

Tested with Rakudo 2015.09 and IRC evalbot Rakudo
2015.11.505.ge.52617.c.

doc/Language/control.pod

@@ -147,19 +147,13 @@ run the block, or it will return the value which the block produces:
     my $c = 0; say (1, (if 1 { $c += 42; 2; }), 3, $c); # says "1 2 3 42"
     my $d = 0; say (1, (if 0 { $d += 42; 2; }), 3, $d); # says "1 3 0"
 
-Implementation note: Currently, Rakudo will say "1 Nil 3 0" for the last
-example because it is not caught up to this part of the design yet.
-
 For the statement modifier it is the same, except you have the value
 of the statement instead of a block:
 
     say (1, (42 if True) , 2); # says "1 42 2"
     say (1, (42 if False), 2); # says "1 2"
     say (1,  42 if False , 2); # says "1 42" because "if False, 2" is true
 
-Implementation note: Currently, Rakudo will say "1 Nil 2" for the second
-example because it is not caught up to this part of the design yet.
-
 The C<if> does not change the topic (C<$_>) by default.  In order to access
 the value which the conditional expression produced, you have to ask
 for it more strongly:
@@ -231,9 +225,6 @@ or the value produced by the block that did run:
                     (if 0 { $d += 42; "two"; } elsif False { $d += 43; 2; }),
                     3, $d); # says "1 3 0"
 
-Implementation note: Currently, Rakudo will say "1 Nil 3 0" for the last
-example because it is not caught up to this part of the design yet.
-
 It's possible to obtain the value of the previous expression inside an
 C<else>, which could be from C<if> or the last C<elsif> if any are
 present: