Consistently use American English spelling

Since the Spring Framework uses American English spelling, this commit
updates Javadoc and the reference manual to ensure consistency in that
regard. However, there are two exceptions to this rule that arise due
to their use within a technical context.

- We use "cancelled/cancelling" instead of "canceled/canceling" in
  numerous places (including error messages).
- We use "implementor" instead of "implementer".

Closes gh-36470

(cherry picked from commit 17699103dc)

spring-orm/src/test/java/org/springframework/orm/jpa/AbstractContainerEntityManagerFactoryIntegrationTests.java

@@ -106,7 +106,7 @@ public abstract class AbstractContainerEntityManagerFactoryIntegrationTests
 	void testGetReferenceWhenNoRow() {
 		assertThatException().isThrownBy(() -> {
 				Person notThere = sharedEntityManager.getReference(Person.class, 666);
-				// We may get here (as with Hibernate). Either behaviour is valid:
+				// We may get here (as with Hibernate). Either behavior is valid:
 				// throw exception on first access or on getReference itself.
 				notThere.getFirstName();
 			})