Bump pglast from 3.4 to 5.1

[dependabot]

Bumps pglast from 3.4 to 5.1.

Changelog

Sourced from pglast's changelog.

5.1 (2023-02-28)

- Merge `version 4.2`__ changes
__ 4.2 (2023-02-27)_
5.0 (2023-02-19)

• No changes

5.0.dev1 (2023-02-11)

- Update libpg_query to `15-4.2.0`__
__ https://github.com/pganalyze/libpg_query/releases/tag/15-4.2.0
**Breaking changes**



Change the type of the ast.Float value from Decimal to str
Using a Decimal implies potential differences in the representation of floating numbers,
and already caused issues ([#91](https://github.com/lelit/pglast/issues/91)__ and [#100](https://github.com/lelit/pglast/issues/100)__) in the past, making it impossible to render,
say, SELECT 0.0e1, due to the fact that Decimal('0.0e1') resolves to
Decimal('0').
__ lelit/pglast#91
__ lelit/pglast#100


5.0.dev0 (2022-12-19)

• No visible changes with respect to v4, apart from the support for new/revised syntaxes of PostgreSQL 15__

  __ https://www.postgresql.org/docs/15/release-15.html

**Breaking changes**

• Target PostgreSQL 15, thanks to libpg_query 15-4.0.0__

... (truncated)

Commits

• 2ee74d4 Release 5.1
• 39b691f Update CHANGES.rst
• 620ea50 Merge from v4
• 57b1a73 Release 4.2
• 164474c Don't ruine the whole CI session if codecov upload fails
• 407e2fa Update CHANGES.rst
• 46c415d Handle special case of TypeCast within a VariableSetStmt
• e81498f Remove outdated FIXME
• 99a523a Handle C longs and doubles respectively as Python ints and floats
• ff06d8f Raise an error on unhandled C types
• Additional commits viewable in compare view

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