Fix the schedule of vectorizer improvement monthly sync

Author: hiraditya

llvm/docs/GettingInvolved.rst

@@ -205,7 +205,7 @@ what to add to your calendar invite.
      - `gcal <https://calendar.google.com/calendar/u/0?cid=c3ljbC5sbHZtLndnQGdtYWlsLmNvbQ>`__
      - `Meeting details/agenda <https://docs.google.com/document/d/1ivYDSn_5ChTeiZ7TiO64WC_jYJnGwAUiT9Ngi9cAdFU/edit?usp=sharing>`__
    * - Vectorizer Improvement Working Group
-     - Every 3rd Thursday of the month
+     - 3rd Tuesday of the month
      - `ics <https://drive.google.com/file/d/1ten-u-4yjOcCoONUtR4_AxsFxRDTUp1b/view?usp=sharing>`__
      - `Meeting details/agenda: <https://docs.google.com/document/d/1Glzy2JiWuysbD-HBWGUOkZqT09GJ4_Ljodr0lXD5XfQ/edit>`__