[BUGFIX] Fix missing single quotes in SchemaMigratorTest

Change-Id: I452252096e39d8986dfa414016011d16f33523b8
Resolves: #49072
Related: #41344
Releases: 6.2
Reviewed-on: https://review.typo3.org/21371
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters