Update translating.md: Minor suggestions
Update translating.md: Minor suggestions

Primarily spelling, wording, and grammar. A little bit of formatting too.
vector-im/riot-web,vector-im/vector-web,vector-im/riot-web,vector-im/vector-web,vector-im/riot-web,martindale/vector,vector-im/riot-web,martindale/vector,vector-im/vector-web,vector-im/riot-web,vector-im/vector-web,vector-im/vector-web,vector-im/riot-web