Deletes last reference to Perl 5

I have actually left the reference when talking about `use v6`. In
fact, it happens to me from time to time, and there's no way to
explain what it does other than referencing this.

I agree with @stmuk that it shouldn't be moved. It serves its purpose,
which is to serve as an introduction *for anyone*, not for Perl 5
users now that all those references have been eliminated. This closes #2191

doc/Language/101-basics.pod6

@@ -9,7 +9,7 @@ the results of each game in the format C<Player1 Player2 | 3:2>, which
 means that C<Player1> won against C<Player2> by 3 to 2 sets. You need a
 script that sums up how many matches and sets each player has won to
 determine the overall winner.
-
+ 
 The input data (stored in a file called C<scores.txt>) looks like this:
 
 =for code :lang<data>
@@ -149,13 +149,11 @@ the declared variable as an C<Array>.  Arrays store ordered lists.
 
 =head3 X<C<hash>>
 
-These two lines of code declare two hashes.  The C<%> sigil marks each
-variable as a C<Hash>.  A C<Hash> is an unordered collection of key-value
-pairs.  Other programming languages call that a I<hash table>,
-I<dictionary>, or I<map>.  You can query a hash table for the value that
-corresponds to a certain C<$key> with C<%hash{$key}>N<Unlike Perl 5, in
-Perl 6 the sigil does not change when accessing an array or hash with
-C<[ ]> or C<{ }>. This is called X<I<sigil invariance>>>.
+These two lines of code declare two hashes.  The C<%> sigil marks each variable
+as a C<Hash>.  A C<Hash> is an unordered collection of key-value pairs.  Other
+programming languages call that a I<hash table>, I<dictionary>, or I<map>.  You
+can query a hash table for the value that corresponds to a certain C<$key> with
+C<%hash{$key}>.
 
 In the score counting program, C<%matches> stores the number of matches each
 player has won.  C<%sets> stores the number of sets each player has won. Both
@@ -355,12 +353,10 @@ sigil as well as blocks of code in curly braces. Since any arbitrary
 Perl code can appear within curly braces, C<Array>s and C<Hash>es may be
 interpolated by placing them within curly braces.
 
-
-Arrays within
-curly braces are interpolated with a single space character between each
-item. Hashes within curly braces are interpolated as a series of
-lines. Each line will contain a key, followed by a tab character, then
-the value associated with that key, and finally a newline.
+Arrays within curly braces are interpolated with a single space character
+between each item. Hashes within curly braces are interpolated as a series of
+lines. Each line will contain a key, followed by a tab character, then the value
+associated with that key, and finally a newline.
 
 Let's see an example of this now.