chore(sdk-node): add notice to manually install '@opentelemetry/exporter-jaeger'

[pichlermarc]

Which problem is this PR solving?

Add a notice that '@opentelemetry/exporter-jaeger' has to be installed manually starting 0.43.0.

Reasoning:

• @opentelemetry/exporter-jaeger is deprecated
• see also fix(sdk-node): move @opentelemetry/exporter-jaeger to dev dependencies #4049 (comment)

This PR is a prerequisite for #4049

Type of change

• (preparing for) breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

• Run postinstall locally

[codecov]

Codecov Report

Merging #4068 (b9301b8) into main (dfe9bdd) will decrease coverage by 0.18%.
Report is 1 commits behind head on main.
The diff coverage is n/a.

❗ Current head b9301b8 differs from pull request most recent head 9f92395. Consider uploading reports for the commit 9f92395 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4068      +/-   ##
==========================================
- Coverage   92.56%   92.38%   -0.18%     
==========================================
  Files         317      321       +4     
  Lines        9213     9276      +63     
  Branches     1957     1970      +13     
==========================================
+ Hits         8528     8570      +42     
- Misses        685      706      +21     

see 5 files with indirect coverage changes