chore: sync v4.3.2 metadata in META.json and README badge

[valehdba]

Trailing miss from the v4.3.2 release identified by the maintainer.

META.json (the PGXN extension metadata) and the README.md shields.io version badge were both still on 4.3.0, dating back to the pre-v4.3.1 work. The control file, C version string, SQL files, and all docs were correctly bumped during the v4.3.1 / v4.3.2 work; only these two surfaces lagged.

What changes

META.json
    - top-level "version":              4.3.0 -> 4.3.2
    - provides.pgclone.file:            "sql/pgclone--4.3.0.sql" -> 4.3.2
    - provides.pgclone.version:         4.3.0 -> 4.3.2
README.md
    - shields.io badge URL + linked release tag:  v4.3.0 -> v4.3.2

4 lines. No code change. No SQL change. No CI behaviour change.

Why it matters

The v4.3.2 source tarball at https://github.com/valehdba/pgclone/archive/refs/tags/v4.3.2.tar.gz currently contains the stale META.json, which would mislead any PGXN tooling consuming this release. After this PR merges I'll move the v4.3.2 tag to include this fix (same retag dance used for v4.3.1 yesterday — the release is fresh enough that nobody has pinned to the current SHA).

What's intentionally NOT changed

Several v4.3.0 / v4.3.1 strings remain in src/pgclone.c, SECURITY.md, and README.md line 147 (the roadmap). These are historical references ("As of v4.3.1, pgclone re-parses every source conninfo…", "v4.3.0: Consistent-snapshot clones…") that document when features shipped, not what version you're on. They should not move with the version bump.

After merge

1. delete refs/tags/v4.3.2
2. recreate v4.3.2 (annotated) at the new main HEAD
3. re-publish the existing Release (auto-demoted to draft by the retag)