chore: update pg_graphql to v1.2.0

[Flambe]

What kind of change does this PR introduce?

Updates pg_graphql to v1.2.0: https://github.com/supabase/pg_graphql/releases/tag/v1.2.0

• feature: String type filters support ilike, like, startsWith
• feature: Support for @Skip and @include directives
• feature: Custom descriptions via comment directive @graphql({"description": ...})
• bugfix: Unknown types are represented in GraphQL schema as Opaque rather than String
• bugfix: PostgreSQL type modifiers, e.g. char(n), no longer truncate excess text
• bugfix: Creating a new enum variant between existing variants no longer errors

I copied how this was done in #509

Closes #596