fix(pg-connection-string): strip brackets from IPv6 host

[spokodev]

Problem

pg-connection-string leaves the URI square brackets on the host for IPv6 literals, so the parsed host is unusable:

const parse = require('pg-connection-string')
parse('postgresql://[::1]:5432/mydb').host       // '[::1]'         (should be '::1')
parse('postgresql://[2001:db8::1]/db').host      // '[2001:db8::1]' (should be '2001:db8::1')

The brackets are RFC 3986 / WHATWG URI delimiters for an IPv6 host, not part of the address. libpq stores the bracket-free literal, and pg passes config.host straight to net.connect / dns.lookup:

pg connection-parameters.js → this.host = '[::1]' → net.connect(port, '[::1]')
→ net.isIP('[::1]') === 0 → dns.lookup('[::1]') → ENOTFOUND

So every IPv6 connection string fails to connect today. There is no test or option covering IPv6, so this is an unguarded gap, not intentional.

Fix

Strip a leading [ / trailing ] from the parsed hostname:

-  const hostname = dummyHost ? '' : result.hostname
+  // The WHATWG URL parser keeps the square brackets around an IPv6 literal
+  // (e.g. [::1]); strip them so config.host is a bare address that libpq, and
+  // node's net.connect / dns.lookup, can use directly.
+  const hostname = (dummyHost ? '' : result.hostname).replace(/^\[(.+)\]$/, '$1')

Unconditional replace (no new branch, keeps 100% branch coverage); a no-op for non-bracketed hosts.

Verification

• New test: postgres://user:pw@[2001:db8::1]:5432/mydb → host 2001:db8::1, port 5432; [::1] → ::1. Fails on master, passes with the fix.
• Confirmed unaffected: IPv4 / DNS hostnames, percent-encoded Unix-socket hosts (%2F...), the ?host= query-param override, and a bracketed database name (%5Bweird%5D stays [weird]).
• Cross-checked against libpq conninfo_uri_parse_options, which advances past [ and NUL-terminates at ] (stores the bare literal).
• Full suite: 80 passing, nyc check-coverage 100% maintained.