Remove secure mode error logic in DnsOverHttpsMode policy

The error logic for DnsOverHttpsMode policy's secure mode is no longer
needed. Remove the logic from the policy handler and update tests to
match the new behavior.

Also, correct the handler's header comment.

Bug: 955454
Change-Id: I6c471116c27f8c25c2f8222b58d4767ab1ef3b56
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2020606
Commit-Queue: Steven Bingler <[email protected]>
Reviewed-by: Julian Pastarmov <[email protected]>
Reviewed-by: Eric Orth <[email protected]>
Cr-Commit-Position: refs/heads/master@{#747917}
diff --git a/chrome/browser/net/secure_dns_policy_handler.h b/chrome/browser/net/secure_dns_policy_handler.h
index 8684d896..ee42cd2 100644
--- a/chrome/browser/net/secure_dns_policy_handler.h
+++ b/chrome/browser/net/secure_dns_policy_handler.h
@@ -13,7 +13,7 @@
 
 namespace policy {
 
-// Handles DnsOverHttpsMode policy.
+// Handles DnsOverHttpsMode and DnsOverHttpsTemplates policies.
 class SecureDnsPolicyHandler : public ConfigurationPolicyHandler {
  public:
   SecureDnsPolicyHandler();