remove inline footnote syntax from sandbox.md

apps/app/resource/locales/en_US/sandbox.md

@@ -401,7 +401,7 @@ Content Cell,Content Cell
 
 # :memo: Footnote
 
-You can write a reference [^1] to a footnote. You can also add an inline footnote^[Inline_footnote].
+You can write a reference [^1] to a footnote.
 
 Long footnotes can be written as [^longnote].
 

apps/app/resource/locales/ja_JP/sandbox.md

@@ -400,7 +400,7 @@ Content Cell,Content Cell
 
 # :memo: Footnote
 
-脚注への参照[^1]を書くことができます。また、インラインの脚注^[インラインで記述できる脚注です]を入れる事も出来ます。
+脚注への参照[^1]を書くことができます。
 
 長い脚注は[^longnote]のように書くことができます。
 

apps/app/resource/locales/zh_CN/sandbox.md

@@ -401,7 +401,7 @@ Content Cell,Content Cell
 
 # :memo: Footnote
 
-You can write a reference [^1] to a footnote. You can also add an inline footnote^[Inline_footnote].
+You can write a reference [^1] to a footnote.
 
 Long footnotes can be written as [^longnote].