fmt: fix a bug that break generics call in string inter (#11468)

vlib/v/ast/str.v

@@ -201,7 +201,7 @@ pub fn (lit &StringInterLiteral) get_fspec_braces(i int) (string, bool) {
 					break
 				}
 				CallExpr {
-					if sub_expr.args.len != 0 {
+					if sub_expr.args.len != 0 || sub_expr.concrete_types.len != 0 {
 						needs_braces = true
 					} else if sub_expr.left is CallExpr {
 						sub_expr = sub_expr.left

vlib/v/fmt/tests/string_interpolation_keep.vv

@@ -14,4 +14,6 @@ fn main() {
 	println('(${some_struct.@type}, $some_struct.y)')
 	_ := 'CastExpr ${int(d.e).str()}'
 	println('${f[0..4].bytestr()}')
+	_ := '${generic_fn<int>()}'
+	_ := '${foo.generic_method<int>()}'
 }