I'm working on updating Three.js and I find that when I upgrade to r125, attempts to set vertices on BufferGeometry fail due to the method missing. It also appears to have removed verticesNeedUpdate. The migration guide does not appear to warn about this and the changelog doesn't seem to address it from what I can see.
I unfortunately didn't write the original code so I'm unsure of how to resolve it. The code looks like this:
this.geometry.vertices[0].x = this.geometry.vertices[2].x = -this.canvas.width / 2;
this.geometry.vertices[1].x = this.geometry.vertices[3].x = this.canvas.width / 2;
this.geometry.vertices[0].y = this.geometry.vertices[1].y = this.canvas.height / 2;
this.geometry.vertices[2].y = this.geometry.vertices[3].y = -this.canvas.height / 2;
this.geometry.verticesNeedUpdate = true;
Update using Don's Answer Below
After applying Don's suggested change, we wind up with this:
const negativeWidth = -this.canvas.width / 2;
const positiveWidth = this.canvas.width / 2;
const positiveHeight = this.canvas.height / 2;
const negativeHeight = -this.canvas.height / 2;
this.geometry.attributes.position.setXY(0, negativeWidth, positiveHeight);
this.geometry.attributes.position.setXY(1, positiveWidth, positiveHeight);
this.geometry.attributes.position.setXY(2, negativeWidth, negativeHeight);
this.geometry.attributes.position.setXY(3, positiveWidth, negativeHeight);
this.geometry.attributes.position.needsUpdate = true;