Fix Maven plugin command-line examples

Fixes gh-21078

Author: scottfrederick

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/docs/asciidoc/packaging-oci-image.adoc

@@ -137,7 +137,7 @@ The builder can be specified on the command line as well, as shown in this examp
 
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-	$ mvn spring-boot:build-image -Dspring-boot.build-image:builder=mine/java-cnb-builder
+	$ mvn spring-boot:build-image -Dspring-boot.build-image.builder=mine/java-cnb-builder
 ----
 
 
@@ -230,6 +230,6 @@ The image name can be specified on the command line as well, as shown in this ex
 
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 ----
-	$ mvn spring-boot:build-image -Dspring-boot.build-image:imageName=example.com/library/v1
+	$ mvn spring-boot:build-image -Dspring-boot.build-image.imageName=example.com/library/v1
 ----