docs(exporter-logs-otlp-proto): Fixup markdown table

[Zirak]

Which problem is this PR solving?

The markdown table in the exporter-logs-otlp-proto README was slightly unformatted. Example screenshot from npmjs:

Here's also a before/after of the file:

Type of change

• This is a small documentation update

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.00%. Comparing base (56df3c0) to head (a96cd02).
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5740      +/-   ##
==========================================
- Coverage   95.04%   95.00%   -0.04%     
==========================================
  Files         310      303       -7     
  Lines        8008     7952      -56     
  Branches     1616     1609       -7     
==========================================
- Hits         7611     7555      -56     
  Misses        397      397              

see 10 files with indirect coverage changes

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[opentelemetrybot]

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