Fixed ref tag path to working solution

Author: daymxn

buildSrc/src/main/java/com/google/firebase/gradle/plugins/DackkaPlugin.kt

@@ -298,15 +298,15 @@ abstract class DackkaPlugin : Plugin<Project> {
         val transformJavadoc = project.tasks.register<FiresiteTransformTask>("firesiteTransformJavadoc") {
             dependsOnAndMustRunAfter("separateJavadoc")
 
-            referenceHeadTagsPath.set("/android")
+            referenceHeadTagsPath.set("docs/reference/android")
             dackkaFiles.set(project.childFile(separatedFilesDirectory, "android"))
             outputDirectory.set(project.childFile(targetDirectory, "android"))
         }
 
         val transformKotlindoc = project.tasks.register<FiresiteTransformTask>("firesiteTransformKotlindoc") {
             dependsOnAndMustRunAfter("separateKotlindoc")
 
-            referenceHeadTagsPath.set("/kotlin")
+            referenceHeadTagsPath.set("docs/reference/kotlin")
             dackkaFiles.set(project.childFile(separatedFilesDirectory, "kotlin"))
             outputDirectory.set(project.childFile(targetDirectory, "kotlin"))
         }