Fix performDragOperation: diagnostic typo

* src/nsterm.m (performDragOperation:): Fix missing newline.
1 job for master in 63 minutes and 2 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #2345
test-all

01:03:02

 
Name Stage Failure
failed
test-all Test
make[2]: *** [check-doit] Error 1
Makefile:318: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
make[1]: *** [check-expensive] Error 2
Makefile:293: recipe for target 'check-expensive' failed
make[1]: Leaving directory '/builds/emacs/emacs/test'
make: *** [check-expensive] Error 2
Makefile:959: recipe for target 'check-expensive' failed
ERROR: Job failed: exit code 1