build(deps): bump protobuf in /libbeat/tests/system (elastic#37662)

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.19.4 to 3.19.5.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](protocolbuffers/protobuf@v3.19.4...v3.19.5)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Craig MacKenzie <craig.mackenzie@elastic.co>

libbeat/tests/system/requirements.txt

@@ -45,7 +45,7 @@ packaging==20.4
 parameterized==0.7.0
 paramiko==3.4.0
 pluggy==0.13.1
-protobuf==3.19.4
+protobuf==3.19.5
 py==1.11.0
 pycodestyle==2.6.0
 pycparser==2.21

libbeat/tests/system/requirements_aix.txt

@@ -45,7 +45,7 @@ packaging==20.4
 parameterized==0.7.0
 paramiko==3.4.0
 pluggy==0.13.1
-protobuf==3.19.4
+protobuf==3.19.5
 py==1.11.0
 pycodestyle==2.6.0
 pycparser==2.21