Fix inconsistencies in @jls tags in java.util.concurrent

The name of JLS section 5.1.2 was changed from "Widening Primitive Conversions" (plural) to "Widening Primitive Conversion" (singular) in Java SE 7.

The @jls tags referring to 5.1.2 in java.util.concurrent should be updated accordingly:

src/java.base/share/classes/java/util/concurrent/atomic/AtomicInteger.java: unexpected: 5.1.2 Widening Primitive Conversions
src/java.base/share/classes/java/util/concurrent/atomic/AtomicLong.java: unexpected: 5.1.2 Widening Primitive Conversions
src/java.base/share/classes/java/util/concurrent/atomic/AtomicLong.java: unexpected: 5.1.3 Narrowing Primitive Conversions