Double quotes forces case sensitive names.
From this blog: Don’t use double quotes in PostgreSQL
Now, there is a way around this, namely by using double quotes. Whereas single quotes in PostgreSQL are used to create a text string, double quotes are used to name an identifier without changing its case.
Let me say that again, because so many people get this wrong: Single quotes and double quotes in PostgreSQL have completely different jobs, and return completely different data types. Single quotes return text strings. Double quotes return (if you can really think of them as “returning” anything) identifiers, but with the case preserved.
In your question you should change:
GRANT SELECT ON ALL TABLES IN SCHEMA requetesql TO ....;
GRANT SELECT ON ALL TABLES IN SCHEMA "requeteSQL" TO ....;