fix(pub): Use the correct option for the Gradle version

Align the code with the documentation to use "gradleVersion" instead of
"Gradle" as the name of the option to configure the Gradle version.

Signed-off-by: Martin Nonnenmacher <martin.nonnenmacher@bosch.com>

plugins/package-managers/pub/src/main/kotlin/Pub.kt

@@ -112,6 +112,7 @@ class Pub(
     repoConfig: RepositoryConfiguration
 ) : PackageManager(name, analysisRoot, analyzerConfig, repoConfig), CommandLineTool {
     companion object {
+        const val OPTION_GRADLE_VERSION = "gradleVersion"
         const val OPTION_PUB_DEPENDENCIES_ONLY = "pubDependenciesOnly"
     }
 
@@ -439,7 +440,7 @@ class Pub(
         if (gradleFactory == null || !definitionFile.isFile) return emptyList()
 
         return analyzerResultCacheAndroid.getOrPut(packageName) {
-            val pubGradleVersion = options[gradleFactory.type] ?: GRADLE_VERSION
+            val pubGradleVersion = options[OPTION_GRADLE_VERSION] ?: GRADLE_VERSION
 
             logger.info {
                 "Analyzing Android dependencies for package '$packageName' using Gradle version $pubGradleVersion."