feat(flink): modify grammar to match keywords

Author: Erindcl

src/grammar/flinksql/FlinkSqlLexer.g4

@@ -127,25 +127,8 @@ TRAILING:                     'TRAILING';
 IF:                           'IF';
 POSITION:                     'POSITION';
 EXTRACT:                      'EXTRACT';
-EQ:                           'EQ';
-NSEQ:                         'NSEQ';
-NEQ:                          'NEQ';
-NEQJ:                         'NEQJ';
-LT:                           'LT';
-LTE:                          'LTE';
-GT:                           'GT';
-GTE:                          'GTE';
-PLUS:                         'PLUS';
 MINUS:                        'MINUS';
-ASTERISK:                     'ASTERISK';
-SLASH:                        'SLASH';
-PERCENT:                      'PERCENT';
 DIV:                          'DIV';
-TILDE:                        'TILDE';
-AMPERSAND:                    'AMPERSAND';
-PIPE:                         'PIPE';
-CONCAT_PIPE:                  'CONCAT_PIPE';
-HAT:                          'HAT';
 PERCENTLIT:                   'PERCENTLIT';
 BUCKET:                       'BUCKET';
 OUT:                          'OUT';
@@ -240,23 +223,14 @@ LOCAL:                        'LOCAL';
 INPATH:                       'INPATH';
 WATERMARK:                    'WATERMARK';
 UNNEST:                       'UNNEST';
-MATCH_RECOGNIZE:              'MATCH_RECOGNIZE';
-MEASURES:                     'MEASURES';
-ONE:                          'ONE';
-PER:                          'PER';
 MATCH:                        'MATCH';
-SKIP1:                        'SKIP1';
 NEXT:                         'NEXT';
-PAST:                         'PAST';
-PATTERN:                      'PATTERN';
 WITHIN:                       'WITHIN';
-DEFINE:                       'DEFINE';
 WS:                           'WS';
 SYSTEM:                       'SYSTEM';
 INCLUDING:                    'INCLUDING';
 EXCLUDING:                    'EXCLUDING';
 CONSTRAINTS:                  'CONSTRAINTS';
-OVERWRITING:                  'OVERWRITING';
 GENERATED:                    'GENERATED';
 CATALOG:                      'CATALOG';
 LANGUAGE:                     'LANGUAGE';