[SPDK] Community calls switching to Skype

Hi all,

In order to keep the Community and GitHub Issue Review meetings running smoothly, they will be now hosted using Skype.
The change was motivated by previous service being increasingly troublesome to join and use with each passing week.

Please see https://spdk.io/community/ for details on joining.
There are no changes to dates or time of the meetings.

Thank you,
Tomek