Mnemonics are set for these actions in the "File" menu
- Recent &Files
- &Restart

It was not possible to set unique mnemonics, now there are duplicated
mnemonics however there are already shortcut keys for the existing
mnemonic actions

Change-Id: I6e3e3ed0cf57601182a315715538b11dbd424b5e
Signed-off-by: Wolfgang Schramm <wolfgang.schramm@gmail.com>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.ui/+/189133
Tested-by: Platform Bot <platform-bot@eclipse.org>
Reviewed-by: Karsten Thoms <karsten.thoms@karakun.com>