Only process main metadata as it already includes additional metadata

Previously, the configuration property table generation was reading
both the main metadata and the additional metadata from each project.
This was unnecessary as the annotation processor will have already
merged the additional metadata into the main metadata before writing
it to disk. Processing both the main and additional metadata led to
a clash as the metadata overlapped. When the entry in the additional
metadata won the clash, the resulting entry in the configuration
property table would lose any details that aren't contained in the
additional metadata.

This commit updates the property table generation code to only use
the main metadata files.

Fixes gh-21131

Author: wilkinsona

spring-boot-project/spring-boot-docs/src/main/groovy/generateConfigurationPropertyTables.groovy

@@ -6,12 +6,8 @@ import java.nio.file.Path
 import java.nio.file.Paths
 
 def getConfigMetadataInputStreams() {
-	def mainMetadata = getClass().getClassLoader().getResources("META-INF/spring-configuration-metadata.json")
-	def additionalMetadata = getClass().getClassLoader().getResources("META-INF/additional-spring-configuration-metadata.json")
-	def streams = []
-	streams += mainMetadata.collect { new UrlResource(it).getInputStream() }
-	streams += additionalMetadata.collect { new UrlResource(it).getInputStream() }
-	return streams
+	return getClass().getClassLoader().getResources("META-INF/spring-configuration-metadata.json")
+			.collect { new UrlResource(it).getInputStream() }
 }
 
 def generateConfigMetadataDocumentation() {