fix ISO 639-1 code for Japanese

"jp" -> "ja"

gallery_dl/extractor/exhentai.py

@@ -128,7 +128,7 @@ class ExhentaiGalleryExtractor(ExhentaiExtractor):
                 "gid": 1200119,
                 "height": int,
                 "image_token": "re:[0-9a-f]{10}",
-                "lang": "jp",
+                "lang": "ja",
                 "language": "Japanese",
                 "parent": "",
                 "rating": r"re:\d\.\d+",

gallery_dl/util.py

@@ -330,7 +330,7 @@ CODES = {
     "hu": "Hungarian",
     "id": "Indonesian",
     "it": "Italian",
-    "jp": "Japanese",
+    "ja": "Japanese",
     "ko": "Korean",
     "ms": "Malay",
     "nl": "Dutch",

test/test_util.py

@@ -134,6 +134,7 @@ class TestISO639_1(unittest.TestCase):
         self._run_test(util.code_to_language, {
             ("en",): "English",
             ("FR",): "French",
+            ("ja",): "Japanese",
             ("xx",): None,
             (""  ,): None,
             (None,): None,
@@ -149,6 +150,7 @@ class TestISO639_1(unittest.TestCase):
         self._run_test(util.language_to_code, {
             ("English",): "en",
             ("fRENch",): "fr",
+            ("Japanese",): "ja",
             ("xx",): None,
             (""  ,): None,
             (None,): None,