D15083: Use title case for the clipboard button

[Nathaniel Graham]

ngraham added reviewers: KDE Applications, broulik, cfeck.

REPOSITORY
  R166 Spectacle

REVISION DETAIL
  https://phabricator.kde.org/D15083

To: ngraham, #spectacle, #kde_applications, broulik, cfeck
Cc: kde-doc-english, skadinna