deps: loosen `pglast` constraint for python 3.11 support

[branchvincent]

This adds support for python 3.11 by loosening the pglast constraint, which fails to build due to a C header longintrepr.h being moved (see https://github.com/python/cpython/issues/79315). To reproduce:

$ poetry env use python3.11
$ poetry install
# ...
clang -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk -I/opt/homebrew/include -I/opt/homebrew/include -I/private/var/folders/1r/p5nhsx151fd7j63p9r1zz4kw0000gn/T/pip-req-build-58dwok55/libpg_query -I/private/var/folders/1r/p5nhsx151fd7j63p9r1zz4kw0000gn/T/pip-req-build-58dwok55/libpg_query/src/postgres/include -I/private/var/folders/1r/p5nhsx151fd7j63p9r1zz4kw0000gn/T/pip-req-build-58dwok55/libpg_query/vendor -I/private/var/folders/1r/p5nhsx151fd7j63p9r1zz4kw0000gn/T/tmp.qP2MtS8D/sgr/.venv/include -I/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/include/python3.11 -c pglast/parser.c -o build/temp.macosx-13-arm64-cpython-311/pglast/parser.o
        pglast/parser.c:282:12: fatal error: 'longintrepr.h' file not found
          #include "longintrepr.h"
                   ^~~~~~~~~~~~~~~
        1 error generated.
        error: command '/usr/bin/clang' failed with exit code 1
        [end of output]

    note: This error originates from a subprocess, and is likely not a problem with pip.
    ERROR: Failed building wheel for pglast
  Failed to build pglast

Note that 3.15 was the first pglast version that officially supported 3.11, but I've left the lower bound untouched (let me know if you'd like something different)

[chenrui333]

cc @neumark

[mildbyte]

Thanks! We'll merge this to trigger the build.