docs: add EDOT SDK encouragement to index and supported-technologies

[alexandra5000]

What does this PR do?

Encourage users to consider the EDOT Java SDK for observability data on the APM agent intro and supported-technologies pages, in line with OTel adoption.

Related to #817

Checklist

~~- [ ] This is an enhancement of existing features, or a new feature in existing plugins

• I have updated CHANGELOG.next-release.md
• I have added tests that prove my fix is effective or that my feature works
• Added an API method or config option? Document in which version this will be introduced~~
• I have made corresponding changes to the documentation
  ~~- [ ] This is a bugfix
• I have updated CHANGELOG.next-release.md
• I have added tests that would fail without this fix
• This is a new plugin
  • I have updated CHANGELOG.next-release.md
  • My code follows the style guidelines of this project~~
    ~~ - [ ] I have made corresponding changes to the documentation
  • I have added tests that prove my fix is effective or that my feature works
  • New and existing unit tests pass locally with my changes
  • I have updated supported-technologies.md
  • Added an API method or config option? Document in which version this will be introduced
  • Added an instrumentation plugin? Describe how you made sure that old, non-supported versions are not instrumented by accident.
• This is something else
  • I have updated CHANGELOG.next-release.md~~

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

2. If you answered "Yes" to the previous question, please specify the tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used: Composer 1.5 via Cursor

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Vale Linting Results

Summary: 1 suggestion found

💡 Suggestions (1)

File	Line	Rule	Message
docs/reference/index.md	15	Elastic.WordChoice	Consider using 'efficient, basic' instead of 'simple', unless the term is in the UI.

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🔍 Preview links for changed docs

• docs/reference/index.md
• docs/reference/supported-technologies.md