Fix typo in ExtensionInstallForcelist policy

"can only" was repeated twice.

Change-Id: I9acf582750dc2f01d700f2c9bacb26c95376df4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2358584Reviewed-by: Owen Min <zmin@chromium.org>
Commit-Queue: Chris Sharp <csharp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798646}

components/policy/resources/policy_templates.json

@@ -4445,7 +4445,7 @@
 
       On <ph name="MS_WIN_NAME">Microsoft® Windows®</ph> instances, apps and extensions from outside the Chrome Web Store can only be forced installed if the instance is joined to a <ph name="MS_AD_NAME">Microsoft® Active Directory®</ph> domain, running on Windows 10 Pro, or enrolled in Chrome Browser Cloud Management.
 
-      On <ph name="MAC_OS_NAME">macOS</ph> instances, apps and extensions from outside the Chrome Web Store can only can only be force installed if the instance is managed via MDM, or joined to a domain via MCX.
+      On <ph name="MAC_OS_NAME">macOS</ph> instances, apps and extensions from outside the Chrome Web Store can only be force installed if the instance is managed via MDM, or joined to a domain via MCX.
 
       The source code of any extension may be altered by users through developer tools, potentially rendering the extension dysfunctional. If this is a concern, set the <ph name="DEVELOPER_TOOLS_DISABLED_POLICY_NAME">DeveloperToolsDisabled</ph> policy.