Fixes typo in the installation instructions

[andreyzb]

Quality checks:

Please check these boxes to confirm this PR covers the following cases:

• Maintaining our upgrade path is essential. Check one or the other:
  • [ ] This PR provides updates via hook_update_N or other means.
  • [x] No updates are necessary for this change.
• Front end fixes should be tested against all of the Open Y Themes.
  • [ ] Tested against Carnation
  • [ ] Tested against Lily
  • [ ] Tested against Rose
  • [x] This change does not contain front-end fixes.
• [x] I have flagged this PR "Needs Review" or pinged the VY devs/QA team in Slack