Update release date

Signed-off-by: Rich Jones <richhones@users.noreply.github.com>

Author: richhones

CHANGES

@@ -1,7 +1,7 @@
 OpenVDB Version History
 =======================
 
-Version 9.1.0 - June 1, 2022
+Version 9.1.0 - June 9, 2022
 
     Bug Fixes:
     - Minor fix to move assignment operator in nanovdb/util/HostBuffer.h.

doc/changes.txt

@@ -4,7 +4,7 @@
 
 @htmlonly <a name="v9_1_0_changes"></a>@endhtmlonly
 @par
-<B>Version 9.1.0</B> - <I>June 1, 2022</I>
+<B>Version 9.1.0</B> - <I>June 9, 2022</I>
 
 @par
 Bug Fixes: