remove ntp app install hint

chrome/browser/resources/ntp4/new_tab_theme.css

Index: chrome/browser/resources/ntp4/new_tab_theme.css
diff --git a/chrome/browser/resources/ntp4/new_tab_theme.css b/chrome/browser/resources/ntp4/new_tab_theme.css
index 7f3cc2105ff7567b76564a313b292b3f117f4dc0..d254598a568db7499899f5fd1f73f858ecefbc56 100644
--- a/chrome/browser/resources/ntp4/new_tab_theme.css
+++ b/chrome/browser/resources/ntp4/new_tab_theme.css
@@ -107,19 +107,3 @@ body {
 .filler .thumbnail {
   border-color: $2;  /* COLOR_NTP_BACKGROUND */
 }
-
-/* App install hint ***********************************************************/
-
-.app-install-hint:hover .app-install-hint-interior > .interior-background,
-.app-install-hint:active .app-install-hint-interior > .interior-background {
-  background-color: rgba($23, 0.2);  /* COLOR_NTP_SECTION_BORDER */
-}
-
-.app-install-hint-interior > .vertical-bar,
-.app-install-hint-interior > .horizontal-bar {
-  background-color: $21;  /* COLOR_NTP_TEXT_LIGHT */
-}
-
-.app-install-hint-interior {
-  border-color: $21;  /* COLOR_NTP_TEXT_LIGHT */
-}