Remove @NullUnmarked

[ronodhirSoumik]

Fixes #17815

[rwinch]

Thanks for the PR @ronodhirSoumik Unfortunately, the build fails.

/home/runner/work/spring-security/spring-security/web/src/main/java/org/springframework/security/web/ObservationFilterChainDecorator.java:323: error: [NullAway] dereferenced expression this.reference.get() is @Nullable
				this.reference.get().error(ex);
				                    ^
    (see http://t.uber.com/nullaway )
/home/runner/work/spring-security/spring-security/web/src/main/java/org/springframework/security/web/ObservationFilterChainDecorator.java:328: error: [NullAway] dereferenced expression this.reference.get() is @Nullable
				this.reference.get().stop();
				                    ^
    (see http://t.uber.com/nullaway )

I've rebased it and fixed the errors and this will be merged once the build passes.

[ronodhirSoumik]

Thanks for the PR @ronodhirSoumik Unfortunately, the build fails.

/home/runner/work/spring-security/spring-security/web/src/main/java/org/springframework/security/web/ObservationFilterChainDecorator.java:323: error: [NullAway] dereferenced expression this.reference.get() is @Nullable
				this.reference.get().error(ex);
				                    ^
    (see http://t.uber.com/nullaway )
/home/runner/work/spring-security/spring-security/web/src/main/java/org/springframework/security/web/ObservationFilterChainDecorator.java:328: error: [NullAway] dereferenced expression this.reference.get() is @Nullable
				this.reference.get().stop();
				                    ^
    (see http://t.uber.com/nullaway )

I've rebased it and fixed the errors and this will be merged once the build passes.

sry I missed the build issue - thanks for pointing it out and for the fix.