Add !important back to .cm-searching and .cm-trailingspace

Those were removed in change I907068f45, causing search results and
trailing whitespaces to not be highlighted in intraline diff chunks.

Change-Id: Ica8f8611cecdd34f0013fa5d3a67929cb1cb139d
diff --git a/gerrit-gwtui/src/main/java/net/codemirror/lib/style.css b/gerrit-gwtui/src/main/java/net/codemirror/lib/style.css
index c5f79d3..6ce70db 100644
--- a/gerrit-gwtui/src/main/java/net/codemirror/lib/style.css
+++ b/gerrit-gwtui/src/main/java/net/codemirror/lib/style.css
@@ -62,11 +62,11 @@
 }
 
 .cm-searching {
-  background-color: #ffa;
+  background-color: #ffa !important;
 }
 
 .cm-trailingspace {
-  background-color: red;
+  background-color: red !important;
 }
 
 /* Line length margin displayed at NN columns to provide