Remove useless and actually harmful 'use lib' statements from modules.

There's no need to use lib 't/spec/packages' in a module that _is_ loaded
from that path already. If t/spec/packages was not in the repo list, we could
not have loaded the modules in the first place.

It's actually harmful as we don't allow a "use lib" in a precompiled module.
This only made it into 6.c as other restrictions prevented us from
precompiling these modules but those restrictions were an implementation
detail, not necessitated by the language design.

packages/A.pm

@@ -1,6 +1,5 @@
 use v6.c;
 
-use lib 't/spec/packages';
 use B;
 class A {
     has B $.x;

packages/A/A.pm

@@ -1,8 +1,6 @@
 use v6.c;
 # used in t/spec/S11-modules/nested.t 
 
-use lib 't/spec/packages';
-
 module A::A {
     use A::B;
 }

packages/B.pm

@@ -1,7 +1,5 @@
 use v6.c;
 
-use lib 't/spec/packages';
-
 use B::Grammar;
 
 class B { 

packages/RoleA.pm

@@ -1,5 +1,4 @@
 use v6.c;
-use lib 't/spec/packages';
 use RoleB;
 
 unit role RoleA;