Remove the "Show solutions" checkbox for tests (a.k.a. gateway guizzes)

Solutions are just shown when they can be.  This is the same as this is
for homework problems.  There is just no reason for the checkbox.

lib/WeBWorK/ContentGenerator/GatewayQuiz.pm

@@ -693,10 +693,8 @@ async sub pre_header_initialize ($c) {
 		showProblemGrader => $c->param('showProblemGrader')
 			|| 0,
 		# Hints are not yet implemented in gateway quzzes.
-		showHints => 0,
-		# showProblemGrader implies showSolutions.  Another convenience for grading.
-		showSolutions => $c->param('showProblemGrader')
-			|| ($c->param('showSolutions') && ($c->{submitAnswers} || $c->{checkAnswers})),
+		showHints     => 0,
+		showSolutions => 1,
 		recordAnswers => $c->{submitAnswers} && !$authz->hasPermissions($userID, 'avoid_recording_answers'),
 		# we also want to check answers if we were checking answers and are switching between pages
 		checkAnswers => $c->{checkAnswers},

templates/ContentGenerator/GatewayQuiz.html.ep

@@ -564,6 +564,17 @@
 						<div class="mb-2"><b><%== maketext('Note: [_1]', tag('i', $pg->{result}{msg})) %></b></div>
 					% }
 					%
+					% if ($pg->{flags}{solutionExists} && $authz->hasPermissions($userID, 'always_show_solution')) {
+						<p>
+							<b><%= maketext('Note') %>:</b>
+							<i>
+								<%= maketext('The solution shown is an instructor preview and '
+									. 'will only be shown to students when answers are available.'
+								) =%>
+							</i>
+						</p>
+					% }
+					%
 					<div class="text-end mb-2">
 						<%= link_to maketext('preview answers') => '#',
 							class => 'gateway-preview-btn btn btn-secondary',
@@ -616,15 +627,6 @@
 					</label>
 				</div>
 			% }
-			% if ($c->{can}{showSolutions}) {
-				<div class="form-check">
-					<label class="form-check-label">
-						<input name="showSolutions" type="checkbox" class="form-check-input"
-							<%= $c->{will}{showSolutions} || $c->{want}{showProblemGrader} ? 'checked' : '' %>>
-						<%= maketext('Show Solutions') %>
-					</label>
-				</div>
-			% }
 			% if ($c->{can}{showProblemGrader}) {
 				<div class="form-check">
 					<label class="form-check-label">