MDL-54649 quiz/question: remove uncessary !important uses

They do not seem at all necessary in testing, so probably just legacy
from lack of css understanding when added.

mod/quiz/styles.css

@@ -1,4 +1,3 @@
-/*csslint important:false */
 /** Bits that can appear on any page. */
 .path-mod-quiz .statedetails {
     display: block;
@@ -426,7 +425,7 @@ body.path-mod-quiz table tbody tr.gradedattempt > td {
 }
 @media print {
     .quiz-secure-window * {
-        display: none !important;
+        display: none;
     }
 }
 
@@ -501,7 +500,7 @@ table.quizreviewsummary td.cell {
 }
 #page-mod-quiz-report table .numcol {
     text-align: center;
-    vertical-align : middle !important;
+    vertical-align : middle;
 }
 
 #page-mod-quiz-report table#attempts {
@@ -530,7 +529,7 @@ table.quizreviewsummary td.cell {
     text-align: left;
 }
 #page-mod-quiz-report table#attempts .picture {
-    text-align: center !important;
+    text-align: center;
 }
 #page-mod-quiz-report table#attempts.grades span.que,
 #page-mod-quiz-report table#attempts span.avgcell {