Make Source Settings Page delegate title smaller

This makes it easier to scan the text as it isn't super big.
2 jobs for master in 5 minutes and 41 seconds (queued for 34 minutes and 27 seconds)
Status Name Job ID Coverage
  Build
passed build_clazy_clang_tidy #153969

00:03:04

passed linux kf5-qt5 qt5.15 #153968

00:02:37

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