Fix documentation of field lookupIfMissing in LookupUnlessProperty

[jesantana]

Fixing javadoc of field lookupIfMissing in LookupUnlessProperty

Closes: #31863

[mkouba]

Actually, I will need to look into the code because I'm not quite sure how this should work for LookupUnlessProperty.

I need to check the code

[gsmet]

I rebased to remove the merge commit.

[quarkus-bot]

Failing Jobs - Building 7d0d4dc

Status	Name	Step	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 11
✔️	JVM Tests - JDK 17
✖	JVM Tests - JDK 17 Windows	Build	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 19

Full information is available in the Build summary check run.

Failures

⚙️ JVM Tests - JDK 17 Windows #

- Failing: extensions/resteasy-classic/rest-client/runtime 
! Skipped: extensions/amazon-lambda-http/deployment extensions/amazon-lambda-http/http-event-server extensions/amazon-lambda-rest/deployment and 104 more

📦 extensions/resteasy-classic/rest-client/runtime

✖ io.quarkus.restclient.runtime.RestClientBaseTest. - More details - Source on GitHub

java.io.IOException: Failed to delete temp directory D:\a\quarkus\quarkus\extensions\resteasy-classic\rest-client\runtime\target\junit8286209118024969923. The following paths could not be deleted (see suppressed exceptions for details): 
	at org.junit.jupiter.engine.extension.TempDirectory$CloseablePath.createIOExceptionWithAttachedFailures(TempDirectory.java:350)
	at org.junit.jupiter.engine.extension.TempDirectory$CloseablePath.close(TempDirectory.java:251)