chore(instrumentation-fastify): mark instrumentation as unmaintained

[pichlermarc]

Which problem is this PR solving?

I had initially picked up ownership for the fastify instrumentation package from a previously unknown owner to keep it alive for a bit longer in case we were to go ahead and remove unmaintained packages.

However, with all the other responsibilities that come with maintaining the JS SIGs two repositories (https://github.com/open-telemetry/opentelemetry-js-contrib, https://github.com/open-telemetry/opentelemetry-js), I don't have a lot of time to dedicate to this instrumentation as other things tend to be higher priority (handling releases, issues, fixing bugs in core components, general repo maintenance). As such, with me as an owner, the instrumentation is effectively unmaintained as I never find enough time to actually work on it. Therefore this PR removes me as an owner to bring more visibility to the fact that this instrumentation is essentially owner-less.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.77%. Comparing base (dfb2dff) to head (630f267).
Report is 246 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2452      +/-   ##
==========================================
- Coverage   90.97%   90.77%   -0.21%     
==========================================
  Files         146      156      +10     
  Lines        7492     7716     +224     
  Branches     1502     1584      +82     
==========================================
+ Hits         6816     7004     +188     
- Misses        676      712      +36     

see 76 files with indirect coverage changes