Fix too strict assert for calldata string -> bytes conversions

test/libsolidity/semanticTests/viaYul/conversion/explicit_string_bytes_calldata_cast.sol

@@ -0,0 +1,11 @@
+// Triggered ICE before
+contract C {
+	function f(string calldata data) external pure returns(string memory) {
+		bytes calldata test = bytes(data[:3]);
+		return string(test);
+	}
+}
+// ====
+// compileViaYul: also
+// ----
+// f(string): 0x20, 3, "123" -> 0x20, 3, "123"