Pin versions of Docker images, update comment

[kinow]

Reasons for creating this PR

From the linked discussion, looks like Varnish changed the image and now it cannot be used with its default port 80. This pull request pins the versions of the images, instead of using the latest tag, in Docker Compose.

Also updates the commented text to avoid YAML errors.

Link to relevant issue(s), if any

• https://groups.google.com/g/skosmos-users/c/9mrL0UhPpco
• unprivileged version varnish/docker-varnish#42

Description of the changes in this PR

Known problems or uncertainties in this PR

Checklist

• phpUnit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if not, explain why below)
• The PR doesn't introduce unintended code changes (e.g. empty lines or useless reindentation)

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
2.6% Duplication

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.68%. Comparing base (5d193c2) to head (e234938).
⚠️ Report is 221 commits behind head on skosmos-2.

Additional details and impacted files

@@             Coverage Diff              @@
##             skosmos-2    #1294   +/-   ##
============================================
  Coverage        70.68%   70.68%           
  Complexity        1646     1646           
============================================
  Files               32       32           
  Lines             3786     3786           
============================================
  Hits              2676     2676           
  Misses            1110     1110           

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[kinow]

Also added some troubleshooting notes to the Wiki: https://github.com/NatLibFi/Skosmos/wiki/Install-Skosmos-with-Fuseki-in-Docker#troubleshooting

[kinow]

Rebased.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.8% Duplication