proposal: remove useless braces

[stephane-archer]

in Dart adding too many braces by accident happens sometimes
while this is valid code, useless braces should be avoided

void bar() {
   log("hello");
}
void foo() {
   {
        bar();
   }
}

in this example, it's quite obvious but when the function is in a class with multiple levels of indentation it's quite hidden.
Here is an example in my code, the closing brace is way lower.