chore(busted) saner default worker_connections

The default hard limit for macOS seems to be 4864 file descriptors, and
cannot be modified easily enough (with a simple `ulimit -n`) so that we
can ask developers to run these commands. Hence, in order to avoid a
warning for each `bin/busted` invocation, let's reduce the default to a
saner value that falls within that range (2^12).

From Kong#3167

bin/busted

@@ -1,6 +1,6 @@
 #!/usr/bin/env resty
 
-local DEFAULT_RESTY_FLAGS="-c 65000"
+local DEFAULT_RESTY_FLAGS="-c 4096"
 
 do
   local lines = getmetatable(io.output()).lines