remove trailing whitespace

Author: coke

doc/Type/Proc/Async.pod6

@@ -75,7 +75,7 @@ along as L<Str|/type/Str>.
         say "Got output '$str' from the external program";
     });
     my $promise = $proc.start;
-    await $promise; 
+    await $promise;
 
 You must call C<stdout> before you call L<#method start>. Otherwise an
 exception of class L<X::Proc::Async::TapBeforeSpawn|/type/X::Proc::Async::TapBeforeSpawn> is
@@ -102,7 +102,7 @@ along as L<Str|/type/Str>.
         say "Got error '$str' from the external program";
     });
     my $promise = $proc.start;
-    await $promise; 
+    await $promise;
 
 You must call C<stderr> before you call L<#method start>. Otherwise an
 exception of class L<X::Proc::Async::TapBeforeSpawn|/type/X::Proc::Async::TapBeforeSpawn> is