mailmap: Fix 'isaacs' for the gen-changelog script

Author: isaacs

.mailmap

@@ -28,7 +28,8 @@ Geoff Flarity <geoff.flarity@gmail.com> <gflarity@raptvm-x02.(none)>
 Gregers Gram Rygg <gregers.gram.rygg@finn.no>
 Ifeanyi Oraelosi <ifeanyioraelosi@gmail.com>
 Isaac Z. Schlueter <i@izs.me> <i@foohack.com>
-Isaac Z. Schlueter <i@izs.me> isaacs <i@izs.me>
+Isaac Z. Schlueter <i@izs.me>
+isaacs <i@izs.me>
 Jake Verbaten <raynos2@gmail.com>
 James Sanders <jimmyjazz14@gmail.com>
 James Treworgy <jamietre@gmail.com>