Fix issues with xss linters

Improve accuracy of javascript-escape linter: Previously this would
match on FOOescape() and FOO.escape calls, but neither are the global
escape function we are worried about.

The regex probably isn't 100% accurate; there may be still false
positives (javascript allows a large range of characters in identifiers,
some of which may not be covered by [\w.$]). The main thing is to avoid
false negatives here though - this will definitely catch any use of
`escape()` or `window.escape()`.

Also remove javascript-interpolate lint - this was deemed unecessary.
StringUtils.interpolate is not in fact safe (it does no html escaping),
so the results of this lint are misleading.

lms/djangoapps/teams/static/teams/js/views/edit_team_members.js

@@ -52,7 +52,7 @@
 
                     _.each(this.model.get('membership'), function(membership) {
                         // eslint-disable-next-line no-undef
-                        dateJoined = interpolate( // xss-lint: disable=javascript-interpolate
+                        dateJoined = interpolate(
                             /* Translators: 'date' is a placeholder for a fuzzy,
                              * relative timestamp (see: https://github.com/rmm5t/jquery-timeago)
                              */
@@ -62,7 +62,7 @@
                         );
 
                         // eslint-disable-next-line no-undef
-                        lastActivity = interpolate( // xss-lint: disable=javascript-interpolate
+                        lastActivity = interpolate(
                             /* Translators: 'date' is a placeholder for a fuzzy,
                              * relative timestamp (see: https://github.com/rmm5t/jquery-timeago)
                              */