Merged in bugfix/SHIBUI-1498 (pull request #431)

SHIBUI-1498 Fixed typo

Approved-by: Bill Smith <wsmith@unicon.net>

backend/src/main/resources/i18n/messages_en.properties

@@ -521,7 +521,7 @@ tooltip.enable-provider-upon-saving=If checkbox is clicked, the metadata provide
 
 tooltip.max-validity-interval=Defines the window within which the metadata is valid.
 tooltip.require-signed-root=If true, this fails to load metadata with no signature on the root XML element.
-tooltip.certificate-file=A path (on the local file system) to a certificate file whose key used to verify the signature. Conflicts with trustEngineRef and both of the child elements.
+tooltip.certificate-file=A path (on the local file system) to a certificate file whose key is used to verify the signature. Conflicts with trustEngineRef and both of the child elements.
 tooltip.retained-roles=Note that property replacement cannot be used on this element.
 tooltip.remove-roleless-entity-descriptors=Controls whether to keep entity descriptors that contain no roles. Note: If this attribute is set to false, the resulting output may not be schema-valid since an <md:EntityDescriptor> element must include at least one role descriptor.
 tooltip.remove-empty-entities-descriptors=Controls whether to keep entities descriptors that contain no entity descriptors. Note: If this attribute is set to false, the resulting output may not be schema-valid since an <md:EntitiesDescriptor> element must include at least one child element, either an <md:EntityDescriptor> element or an <md:EntitiesDescriptor> element.