Fix #3092: Remove splunk-sink, splunk-source and json-patch-action, whose components Camel 4.23 removed

[davsclaus]

Claude Code on behalf of Claus Ibsen.

Fixes #3092. Camel 4.23.0, which main builds against, removed both components these Kamelets use:

Camel component	Removed in apache/camel	Kamelets removed here
camel-splunk	53912a500d66 "Removal of Splunk"	splunk-sink, splunk-source
camel-json-patch	2c538511af7f "Removal of json-patch component"	json-patch-action

This is the case #2890 decided to wait for ("keep as-is until Camel actually removes these components"). paho, also in #2890, is still in Camel, so the mqtt-* Kamelets stay.

Removed:

• the three Kamelets, in kamelets/ and library/camel-kamelets/src/main/resources/kamelets/;
• their pipe templates, in templates/pipes/camel-k/ and templates/pipes/core/;
• docs/modules/ROOT/partials/splunk-source-description.adoc;
• the splunk-sink and splunk-source header checks in KameletsCatalogTest.

nav.adoc and camel-kamelets-catalog-sbom.json are regenerated by the build. ./mvnw verify passes.

For the release notes:

• Splunk HEC publishing stays covered by splunk-hec-sink.
• Splunk search (splunk-source) and JSON Patch (json-patch-action) have no replacement in Camel 4.23.
• The 4.22.x line keeps all three, since Camel 4.22 still has both components.