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

spring-context/src/main/java/org/springframework/context/annotation/ImportAwareAotBeanPostProcessor.java

@@ -30,7 +30,7 @@ import org.springframework.core.type.classreading.MetadataReaderFactory;
 import org.springframework.util.ClassUtils;
 
 /**
- * A {@link BeanPostProcessor} that honours {@link ImportAware} callback using
+ * A {@link BeanPostProcessor} that honors {@link ImportAware} callback using
  * a mapping computed at build time.
  *
  * @author Stephane Nicoll

spring-context/src/main/java/org/springframework/scheduling/concurrent/ScheduledExecutorFactoryBean.java

@@ -39,7 +39,7 @@ import org.springframework.util.ObjectUtils;
  *
  * <p>Allows for registration of {@link ScheduledExecutorTask ScheduledExecutorTasks},
  * automatically starting the {@link ScheduledExecutorService} on initialization and
- * canceling it on destruction of the context. In scenarios that only require static
+ * cancelling it on destruction of the context. In scenarios that only require static
  * registration of tasks at startup, there is no need to access the
  * {@link ScheduledExecutorService} instance itself in application code at all;
  * {@code ScheduledExecutorFactoryBean} is then just being used for lifecycle integration.