wrapped in single quotes for @highlight in snippets

Change-Id: I429afe4210a7024b2a0297e7497cc900109324c5
Signed-off-by: Kalyan Prasad Tatavarthi <kalyan_prasad@in.ibm.com>
Reviewed-on: https://git.eclipse.org/r/c/jdt/eclipse.jdt.core/+/190268
Tested-by: Vikas Chandra <Vikas.Chandra@in.ibm.com>
Tested-by: JDT Bot <jdt-bot@eclipse.org>
Reviewed-by: Vikas Chandra <Vikas.Chandra@in.ibm.com>