.mailmap: specify spelling for Henri Verbeet

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/1999>
diff --git a/.mailmap b/.mailmap
index 193a437..d481f76 100644
--- a/.mailmap
+++ b/.mailmap
@@ -241,6 +241,8 @@
 
 Heinrich Fink <heinrich.fink@daqri.com>
 
+Henri Verbeet <hverbeet@gmail.com>
+
 Homer Hsing <dongsheng.xing@intel.com> <homer.hsing@gmail.com>
 
 Hui Qi Tay <hqtay@vmware.com> <tayhuiqithq@gmail.com>