Fix lexers check when built with newer Go (#928)

Newer versions of Go emit '\f' rather than "\u000c" for formfeeds. This
patch adjusts the expected values for the lexers tests to match.

Fixes: #927

See also: golang/go#64346 for the change to
Go.

Signed-off-by: W. Michael Petullo <mike@flyn.org>

lexers/testdata/python2/test_complex_file1.expected

@@ -170,7 +170,7 @@
   {"type":"Punctuation","value":"("},
   {"type":"Name","value":"translation"},
   {"type":"Punctuation","value":"))"},
-  {"type":"Text","value":"\n\n\n\u000c\n"},
+  {"type":"Text","value":"\n\n\n\f\n"},
   {"type":"CommentSingle","value":"# Base64 encoding/decoding uses binascii"},
   {"type":"Text","value":"\n\n"},
   {"type":"Keyword","value":"def"},
@@ -417,7 +417,7 @@
   {"type":"Punctuation","value":"("},
   {"type":"Name","value":"_urlsafe_decode_translation"},
   {"type":"Punctuation","value":"))"},
-  {"type":"Text","value":"\n\n\n\u000c\n"},
+  {"type":"Text","value":"\n\n\n\f\n"},
   {"type":"CommentSingle","value":"# Base32 encoding/decoding must be done in Python"},
   {"type":"Text","value":"\n"},
   {"type":"Name","value":"_b32alphabet"},
@@ -1458,7 +1458,7 @@
   {"type":"Punctuation","value":"("},
   {"type":"Name","value":"parts"},
   {"type":"Punctuation","value":")"},
-  {"type":"Text","value":"\n\n\n\u000c\n"},
+  {"type":"Text","value":"\n\n\n\f\n"},
   {"type":"CommentSingle","value":"# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns"},
   {"type":"Text","value":"\n"},
   {"type":"CommentSingle","value":"# lowercase.  The RFC also recommends against accepting input case"},
@@ -1541,7 +1541,7 @@
   {"type":"Punctuation","value":"("},
   {"type":"Name","value":"s"},
   {"type":"Punctuation","value":")"},
-  {"type":"Text","value":"\n\n\n\u000c\n"},
+  {"type":"Text","value":"\n\n\n\f\n"},
   {"type":"CommentSingle","value":"# Legacy interface.  This code could be cleaned up since I don't believe"},
   {"type":"Text","value":"\n"},
   {"type":"CommentSingle","value":"# binascii has any line length limitations.  It just doesn't seem worth it"},
@@ -1806,7 +1806,7 @@
   {"type":"Punctuation","value":"("},
   {"type":"Name","value":"s"},
   {"type":"Punctuation","value":")"},
-  {"type":"Text","value":"\n\n\n\u000c\n"},
+  {"type":"Text","value":"\n\n\n\f\n"},
   {"type":"CommentSingle","value":"# Useable as a script..."},
   {"type":"Text","value":"\n"},
   {"type":"Keyword","value":"def"},