Update httpclient.version to v5.6

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
org.apache.httpcomponents.client5:httpclient5-fluent (source)	5.5.2 -> 5.6
org.apache.httpcomponents.client5:httpclient5-cache (source)	5.5.2 -> 5.6
org.apache.httpcomponents.client5:httpclient5 (source)	5.5.2 -> 5.6

---

Release Notes

apache/httpcomponents-client (org.apache.httpcomponents.client5:httpclient5-fluent)

v5.6

This is the first ALPHA release in the 5.6 release series. It adds several features
such as transport content decompression and content compression for the async transport,
support for Unix sockets, experimental support for SCRAM-SHA-256 authentication scheme,
and Micrometer/OTel observations & metrics.

Commons Compress, Brotli codec, and ZStd codec are optional dependencies and get
wired into the execution pipeline only if present on the classpath.

Notable changes and features included in the 5.6 series:

• Unix domain socket support.

• Support for pluggable content codecs via Commons-Compress in the classic transport.
  (optional).

• Support for transparent content decompression and content compression with deflate,
  gzip, zstd (optional), and brotli (optional) codecs in the async transport.

• Micrometer/OTel observations & metrics (optinal).

• Off-lock connection disposal by the classic pooling connection manager. Experimental.

• SCRAM-SHA-256 authentication scheme (RFC 7804). Experimental.

• Request Priority support (RFC 9218). Experimental.

Compatibility notes:

• As of this version, HttpClient uses BUILTIN HostnameVerificationPolicy by default, delegating
  host verification to JSSE security manager. One must explicitly configure the TLS strategy
  to continue using the hostname verifier shipped with HttpClient.

• Five-second TCP keep-alive is now enabled by default.

---

Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about these updates again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.