fix grammar error in im js sdk
fix grammar error in im js sdk

jpush/jpush-docs,jpush/jpush-docs,Aoyunyun/jpush-docs,raoxudong/jpush-docs,Aoyunyun/jpush-docs,Aoyunyun/jpush-docs,xiongtiancheng/jpush-docs,jpush/jpush-docs,jpush/jpush-docs,raoxudong/jpush-docs,raoxudong/jpush-docs,Aoyunyun/jpush-docs,raoxudong/jpush-docs,xiongtiancheng/jpush-docs,xiongtiancheng/jpush-docs,xiongtiancheng/jpush-docs