This pr avoids more false positive throws in MethodThrowsVisitor.
In MethodThrowsVisitor.checkInsn(), there are two places that call visitThrows() to add throws, and the other two places that call filterExceptions() to add throws.

Only visitThrows() calls isThrowsRequired() to ignore runtime exceptions, so sometimes filterExceptions() adds redundant throws.

visitThrows() and filterExceptions() are very similar, the only difference is that the former has two more conditions: excType.isTypeKnown() && isThrowsRequired(mth, excType). So I think it's safe to replace the latter with the former.

A small reproducible example is added.

    public void noThrownExceptions3() {
		// This line leads to false positive throws.
		// 1. assignment 2. invoked method throws runtime exception
        int i = doSomething3(0);
        System.out.print(i);
    }
    public int doSomething3(int i) throws IllegalArgumentException {
        if (i < 0) {
            throw new IllegalArgumentException();
        }
        return 1;
    }