Fix missing entries in TSMS dump

This CL fixes another regression that was introduced when we enabled
multiple users to use spell checker APIs at the same time [1].

Somehow TextServicesManagerService#mOnGoingSessionRequests were not
fully dumped into dumpsys due to an unnecessary '++j' in the loop.

 [1]: I06c27ef834203a21cc445dc126602c799384527b
      06a26240

Bug: 63041121
Test: Manually verified that 'adb shell dumpsys textservices' dumps
      all the elements in #mOnGoingSessionRequests.
Change-Id: Ia26ab1c8ca19e74aaefb8562fb06ff64c3d8d677