This patch updates certain error messages to eliminate spelling
mistakes. No need for a test as this is a minor cosmetic fix.

2019-07-10  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* sem_ch3.adb (Check_Nonoverridable_Aspects): Correct the
	spelling in certain error messages.
	(Check_Pragma_Implemented): Correct the spelling in certain
	error messages.

From-SVN: r273341