PRIMARY in index hint list

[GuptaManan100]

Description

This PR fixes the regression created in release 9.0 due to moving PRIMARY from non-reserved to reserved keywords

• Vitess 8.0

  > SELECT id FROM blog_posts USE INDEX (PRIMARY) WHERE id = 10;
  +------+
  |   id |
  |------|
  |   10 |
  +------+
  1 row in set
  Time: 0.004s
  

• Vitess 9.0

  > SELECT id FROM blog_posts USE INDEX (PRIMARY) WHERE id = 10;
  (1105, "vtgate: http://vtgate:15000/: syntax error at position 67 near 'PRIMARY'")
  

Related Issue(s)

Fixes #8148

Checklist

• Tests were added or are not required
• Documentation was added or is not required