ada: Refactor: replace uses of `not Present(X)` with `No (X)`

ada: Refactor: replace uses of `not Present(X)` with `No (X)`

`No (X)` is essentially `not Present (X)`, there's no reason for not
using this shorter form.

gcc/ada/

	* checks.adb, exp_atag.adb, exp_attr.adb, exp_ch4.adb, exp_ch6.adb,
	exp_ch7.adb, exp_dbug.adb, exp_disp.adb, exp_unst.adb, exp_util.adb,
	freeze.adb, layout.adb, pprint.adb, rtsfind.adb, sem_aggr.adb,
	sem_attr.adb, sem_case.adb, sem_ch12.adb, sem_ch13.adb, sem_ch3.adb,
	sem_ch5.adb, sem_ch6.adb, sem_ch8.adb, sem_dim.adb, sem_prag.adb,
	sem_util.adb, sem_warn.adb:
	Replace uses of `not Present (X)` with `No (X)`.