Voltage rating for SMD Resistor
You have two of these resistor in series, so their voltage capability adds.  Each is good for 300 V, so together they are good for 600 V.

You say the input is 230 V AC, presumably sine.  That means the peaks are 325 V.  For insulation, it's the peak voltage that matters.

Since 325 V is less than 600 V, you are OK in theory.  In practice, stuff happens.  The 230 V in might actually be 240 V, so the peak would be 340 V.  That still gives you 260 V of margin.  Power line spikes also happen.  You are OK up to a 260 V spike at the peak of the waveform.  Is that good enough for you?  Only you can answer that.  To paraphrase Dirty Harry: Do you feel lucky?  Well, do ya, punk?

Another issue is that the 300 V specified by Vishay only applies if you follow all the rules, including the right separation between pads.  The board also needs to be clean, and other traces shouldn't be running closer than some minimum for the voltage you are trying to withstand.

Then there are regulatory issues.  It depends on how and where the equipment will be used.  Different minimum creapage and clearance distances apply depending on what standard you want to claim compatibility with.