[build] use local opencv docs element-list (#8633)

Fixes opencv cloudflare blocking gradle javadoc builds

docs/opencv/element-list

@@ -0,0 +1,29 @@
+org.opencv.aruco
+org.opencv.bgsegm
+org.opencv.bioinspired
+org.opencv.calib3d
+org.opencv.core
+org.opencv.dnn
+org.opencv.dnn_superres
+org.opencv.face
+org.opencv.features2d
+org.opencv.highgui
+org.opencv.img_hash
+org.opencv.imgcodecs
+org.opencv.imgproc
+org.opencv.ml
+org.opencv.objdetect
+org.opencv.osgi
+org.opencv.phase_unwrapping
+org.opencv.photo
+org.opencv.plot
+org.opencv.structured_light
+org.opencv.text
+org.opencv.tracking
+org.opencv.utils
+org.opencv.video
+org.opencv.videoio
+org.opencv.wechat_qrcode
+org.opencv.xfeatures2d
+org.opencv.ximgproc
+org.opencv.xphoto