Update nixpkgs to get PostgreSQL 16

[steve-chavez]

This is so we can postgresql_16 from nixpkgs. However:

• pg_graphql
• pg_jsonschema

Are failing to compile with:

error: builder for '/nix/store/iwrmn62xix5yk4kkpzmb4555hlifpvfk-pg_graphql-unstable-2023-08-01.drv' failed with exit code 1;
       last 10 log lines:
       >   11: main<unknown>
       >       at <unknown source file>:<unknown line>
       >   12: __libc_start_call_main<unknown>
       >       at <unknown source file>:<unknown line>
       >   13: __libc_start_main@@GLIBC_2.34<unknown>
       >       at <unknown source file>:<unknown line>
       >   14: _start<unknown>
       >       at <unknown source file>:<unknown line>
       >
       > Run with COLORBT_SHOW_HIDDEN=1 environment variable to disable frame filtering.
       For full logs, run 'nix log /nix/store/iwrmn62xix5yk4kkpzmb4555hlifpvfk-pg_graphql-unstable-2023-08-01.drv'.

error: builder for '/nix/store/a2zdya2gjii43ncpb35ch9yal0l33pdq-pg_jsonschema-unstable-2023-07-23.drv' failed with exit code 1;
       last 10 log lines:
       >   11: main<unknown>
       >       at <unknown source file>:<unknown line>
       >   12: __libc_start_call_main<unknown>
       >       at <unknown source file>:<unknown line>
       >   13: __libc_start_main@@GLIBC_2.34<unknown>
       >       at <unknown source file>:<unknown line>
       >   14: _start<unknown>
       >       at <unknown source file>:<unknown line>
       >
       > Run with COLORBT_SHOW_HIDDEN=1 environment variable to disable frame filtering.
       For full logs, run 'nix log /nix/store/a2zdya2gjii43ncpb35ch9yal0l33pdq-pg_jsonschema-unstable-2023-07-23.drv'.

Something about GLIBC_2.34.

[steve-chavez]

Looks like pgrx does depend on GLIBC: https://docs.rs/pgrx-pg-sys/latest/pgrx_pg_sys/constant.__GLIBC__.html

[steve-chavez]

For now the only option I see is to update cargo-pgrx and see if the problems goes away

This was previously done on #27