Fix typo in documentation of stripe client (#1401)

This fixes the typo of `mangers` to be `managers` in the documentation
for the `default_connection_managers` method on the `ThreadContext`
class in `lib/stripe/stripe_client.rb`.

Co-authored-by: prathmesh-stripe <165320323+prathmesh-stripe@users.noreply.github.com>

lib/stripe/stripe_client.rb

@@ -366,7 +366,7 @@ class ThreadContext
       # garbage in `Thread.current`.
       attr_accessor :last_responses
 
-      # A map of connection mangers for the thread. Normally shared between
+      # A map of connection managers for the thread. Normally shared between
       # all `StripeClient` objects on a particular thread, and created so as to
       # minimize the number of open connections that an application needs.
       def default_connection_managers