Revert adding messaging category

- This should have been it's own commit
- We want to ensure we get all projects that are messaging at once

Author: rwinch

src/helpers/related_projects.js

@@ -235,19 +235,9 @@ function relatedProjects (categories = [], projectIds = []) {
     { href: 'https://docs.spring.io/spring-ai/reference/', id: 'ai', text: 'Spring AI' },
     { href: 'https://docs.spring.io/spring-cli/reference/', id: 'cli', text: 'Spring CLI' },
     { href: 'https://docs.spring.io/spring-graphql/reference/', id: 'graphql', text: 'Spring GraphQL' },
-    {
-      href: 'https://docs.spring.io/spring-kafka/reference/',
-      id: 'kafka',
-      text: 'Spring for Apache Kafka',
-      categories: ['messaging'],
-    },
+    { href: 'https://docs.spring.io/spring-kafka/reference/', id: 'kafka', text: 'Spring for Apache Kafka' },
     { href: 'https://docs.spring.io/spring-modulith/reference/', id: 'modulith', text: 'Spring Modulith' },
-    {
-      href: 'https://docs.spring.io/spring-pulsar/reference/',
-      id: 'pulsar',
-      text: 'Spring for Apache Pulsar',
-      categories: ['messaging'],
-    },
+    { href: 'https://docs.spring.io/spring-pulsar/reference/', id: 'pulsar', text: 'Spring for Apache Pulsar' },
     { href: 'https://docs.spring.io/spring-shell/reference/', id: 'shell', text: 'Spring Shell' },
   ]
   return projectDocumentation.filter(