Clean up #included files in parser directory (#1465)

[jrgemignani]

Cleaned up #included files in the .c files in the parser directory. Additionally, fixed one that was at the backend root.

modified:   src/backend/age.c
modified:   src/backend/parser/cypher_analyze.c
modified:   src/backend/parser/cypher_clause.c
modified:   src/backend/parser/cypher_expr.c
modified:   src/backend/parser/cypher_gram.y
modified:   src/backend/parser/cypher_item.c
modified:   src/backend/parser/cypher_keywords.c
modified:   src/backend/parser/cypher_parse_node.c
modified:   src/backend/parser/cypher_parser.c

[MuhammadTahaNaveed]

@jrgemignani Is there a need for PRs on PG16 when it is already merged in master(which is PG16 now)?

[jrgemignani]

@jrgemignani Is there a need for PRs on PG16 when it is already merged in master(which is PG16 now)?

Yes. I'm going to start the release process for PG16 -> PG11. So, they need all need to be at the same point.