Fix many spelling mistakes

bin/get-translatable-strings

config-templates/authsources.php

config-templates/config.php

docs/simplesamlphp-authproc.md

docs/simplesamlphp-changelog.md

docs/simplesamlphp-database.md

docs/simplesamlphp-googleapps.md

docs/simplesamlphp-metadata-extensions-attributes.md

docs/simplesamlphp-metadata-extensions-rpi.md

docs/simplesamlphp-modules.md

docs/simplesamlphp-reference-idp-hosted.md

docs/simplesamlphp-sp.md

docs/simplesamlphp-upgrade-notes-1.16.md

docs/simplesamlphp-upgrade-notes-1.17.md

docs/simplesamlphp-upgrade-notes-1.5.md

docs/simplesamlphp-upgrade-notes-1.6.md

docs/simplesamlphp-upgrade-notes-1.9.md

docs/simplesamlphp-upgrade-notes-2.0.md

locales/af/LC_MESSAGES/messages.po

locales/ar/LC_MESSAGES/messages.po