DEV: upgrade redis-namespace gem

New release has a few extra commands namespaced, nothing we use.

Also added a comment about why this is explicitly required.

Gemfile

@@ -43,6 +43,13 @@ gem 'mini_mime'
 gem 'mini_suffix'
 
 gem 'redis'
+
+# This is explicitly used by Sidekiq and is an optional dependency.
+# We tell Sidekiq to use the namespace "sidekiq" which triggers this
+# gem to be used. There is no explicit dependency in sidekiq cause
+# redis namespace support is optional
+# We already namespace stuff in DiscourseRedis, so we should consider
+# just using a single implementation in core vs having 2 namespace implementations
 gem 'redis-namespace'
 
 # NOTE: AM serializer gets a lot slower with recent updates

Gemfile.lock

@@ -309,7 +309,7 @@ GEM
       optimist (>= 3.0.0)
     rchardet (1.8.0)
     redis (4.1.3)
-    redis-namespace (1.6.0)
+    redis-namespace (1.7.0)
       redis (>= 3.0.4)
     request_store (1.4.1)
       rack (>= 1.4)