Simplify a .mailmap entry

Only one person committed with these email addresses, so there's no need to use
the map-different-names-for-one-email-address syntax.

No behavior change.

Differential Revision: https://reviews.llvm.org/D108007

.mailmap

@@ -28,9 +28,8 @@
 <[email protected]> <[email protected]>
 <[email protected]> <[email protected]>
 <[email protected]> <[email protected]>
-Jon Roelofs <[email protected]> Jon Roelofs <[email protected]>
-Jon Roelofs <[email protected]> Jonathan Roelofs <[email protected]>
-Jon Roelofs <[email protected]> Jonathan Roelofs <[email protected]>
+Jon Roelofs <[email protected]> <[email protected]>
+Jon Roelofs <[email protected]> <[email protected]>
 LLVM GN Syncbot <[email protected]>
 Martin Storsjö <[email protected]>
 Saleem Abdulrasool <[email protected]> <[email protected]>