Add extra space around &by param

To make it more obvious it's a positional param, as some reportedly[^1]
try to use it as a named arg.

[1] https://rt.perl.org/Ticket/Display.html?id=130517#ticket-history

Author: zoffixznet

doc/Type/Any.pod6

@@ -129,7 +129,7 @@ Examples:
 Defined as:
 
     multi method sort()
-    multi method sort(&by)
+    multi method sort( &by )
 
 Sorts iterables with C<infix:<cmp>> or given code object and returns a new C<List>.
 
@@ -406,7 +406,7 @@ Coerce the invocant first to a C<List> and then to a L<Supply|/type/Supply>.
 Defined As:
 
     multi method min(--> Any:D)
-    multi method min(&by --> Any:D)
+    multi method min( &by --> Any:D)
 
 Coerces to Iterable and returns the numerically smallest element. If a
 C<Callable> is provided it is called with each element and its smallest return
@@ -417,7 +417,7 @@ values is returned.
 Defined As:
 
     multi method max(--> Any:D)
-    multi method max(&by --> Any:D)
+    multi method max( &by --> Any:D)
 
 Coerces to Iterable and returns the numerically biggest element. If a
 C<Callable> is provided it is called with each element and its biggest return
@@ -428,7 +428,7 @@ values is returned.
 Defined As:
 
     multi method minmax(--> List:D)
-    multi method minmax(&by --> List:D)
+    multi method minmax( &by --> List:D)
 
 Returns a list containing the smallest and the biggest element. If a
 C<Callable> is provided each element is filtered and then numerically compared.