Fix spelling of the word "interstitial"

No one can spell this word, so there are typos all over. Fix them.

BUG=760759

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_site_isolation
Change-Id: Ie8b3678e5f8d0ecedf91dfd06aba743295bdcb93
Reviewed-on: https://chromium-review.googlesource.com/665997
Commit-Queue: Adrienne Porter Felt <[email protected]>
Reviewed-by: Tao Bai <[email protected]>
Reviewed-by: Matt Menke <[email protected]>
Reviewed-by: Jialiu Lin <[email protected]>
Reviewed-by: Charlie Reis (slow) <[email protected]>
Cr-Commit-Position: refs/heads/master@{#501958}
diff --git a/components/security_interstitials_strings.grdp b/components/security_interstitials_strings.grdp
index 3063835..c39d99d 100644
--- a/components/security_interstitials_strings.grdp
+++ b/components/security_interstitials_strings.grdp
@@ -289,7 +289,7 @@
     You can <ph name="BEGIN_ERROR_LINK">&lt;a href="#" id="report-error-link"&gt;</ph>report a detection problem<ph name="END_ERROR_LINK">&lt;/a&gt;</ph> or, if you understand the risks to your security, <ph name="BEGIN_LINK">&lt;a href="#" id="proceed-link"&gt;</ph>visit this unsafe site<ph name="END_LINK">&lt;/a&gt;</ph>.
   </message>
 
-  <!-- WebView Safe Browsing quiet interstitals medium sized -->
+  <!-- WebView Safe Browsing quiet interstitials medium sized -->
   <message name="IDS_MALWARE_WEBVIEW_HEADING" desc="The heading of the malware interstitial on medium sized Webview.">
     Dangerous content blocked.
   </message>