Sentry: Increase disk space

Following [1], the riverside node now uses its own kafka. Its disk grew a bit fast, so we need to extend it a bit [2]

• [1] #2888 (closed)

• [2]

root@riverside:~# df -h /
  Filesystem                      Size  Used Avail Use% Mounted on
  /dev/mapper/riverside--vg-root   28G   26G  576M  98% /

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Migrated from T2898 (view on Phabricator)