Fix typo (#4106)

core/src/main/resources/lib/form/optionalProperty.jelly

@@ -35,7 +35,7 @@ THE SOFTWARE.
     <st:attribute name="title" use="required" />
   </st:documentation>
   <!--
-    Without @checked, optionalBlock will try to coarse an object to a boolean, which fails,
+    Without @checked, optionalBlock will try to coerce an object to a boolean, which fails,
     so override @checked manually.
   -->
   <f:optionalBlock field="${field}" title="${title}" checked="${instance[field]!=null}">
@@ -43,4 +43,4 @@ THE SOFTWARE.
     <j:set var="instance" value="${instance[field]}"/>
     <st:include from="${descriptor}" page="${descriptor.configPage}" />
   </f:optionalBlock>
-</j:jelly>
\ No newline at end of file
+</j:jelly>