i18n: Update Japanese (ja) translations (#2100)

Author: dbrock98

src/gherkin-languages.json

@@ -1885,13 +1885,15 @@
   "ja": {
     "and": [
       "* ",
+      "且つ",
       "かつ"
     ],
     "background": [
       "背景"
     ],
     "but": [
       "* ",
+      "然し",
       "しかし",
       "但し",
       "ただし"
@@ -1911,7 +1913,7 @@
     "name": "Japanese",
     "native": "日本語",
     "rule": [
-      "Rule"
+      "ルール"
     ],
     "scenario": [
       "シナリオ"