Bug 1238781: Add pre-processed pref file to .eslintignore. r=felipe

--HG--
extra : commitid : FulAh3Xj577
extra : rebase_source : 11cf6c7805968ae95428759148414211300c72c3

.eslintignore

@@ -201,6 +201,7 @@ toolkit/content/contentAreaUtils.js
 toolkit/content/widgets/videocontrols.xml
 toolkit/components/jsdownloads/src/DownloadIntegration.jsm
 toolkit/components/search/nsSearchService.js
+toolkit/components/telemetry/healthreport-prefs.js
 toolkit/components/url-classifier/**
 toolkit/components/urlformatter/nsURLFormatter.js
 toolkit/identity/FirefoxAccounts.jsm