protobuf dependencies are missing on the clean machine

[vlntb]

Context of Change

This was discovered while configuring a clean Ubuntu machine to run rippled. Two dependencies to support protobuf types are missing: libprotobuf-dev protobuf-compiler. The update is only relevant for manually configuring the C++ development environment.

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (non-breaking change that only restructures code)
• [ ] Performance (increase or change in throughput and/or latency)
• [ ] Tests (you added tests for code that already exists, or your new feature included in this PR)
• [x] Documentation update
• [ ] Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• [ ] Release

API Impact

• [ ] Public API: New feature (new methods and/or new fields)
• [ ] Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• [ ] libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• [ ] Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 76.1%. Comparing base (63209c2) to head (3e51bbe). Report is 4 commits behind head on develop.

Additional details and impacted files

[](https://app.codecov.io/gh/XRPLF/rippled/pull/5156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF) ```diff @@ Coverage Diff @@ ## develop #5156 +/- ## ========================================= - Coverage 76.1% 76.1% -0.0% ========================================= Files 762 762 Lines 61469 61469 Branches 8121 8122 +1 ========================================= - Hits 46807 46803 -4 - Misses 14662 14666 +4 ``` [see 5 files with indirect coverage changes](https://app.codecov.io/gh/XRPLF/rippled/pull/5156/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF) [](https://app.codecov.io/gh/XRPLF/rippled/pull/5156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF)