Parse a module that has more than 2 lines of comments for a Secret causes a parse error

[gak]

Saw this in TestParseModule when working on #1505 but didn't investigate.

// A comment
module todo {
  // A config value
  config configValue String
  // Shhh
  // This is a secret
  // It should not be shared
  secret secretValue String

schema_test.go:459: Did not expect an error but got:
        9:3: unexpected token "secret" (expected "data" <ident> ("<" TypeParameter ("," TypeParameter)* ">")? "{" Field* "}" Metadata*)