fix mat3x4f offset computer

Author: greggman

webgpu/lessons/resources/js/wgsl-data-types.js

@@ -32,8 +32,8 @@ const b = {
   mat4x3h: { numElements: 16, align:  8, size: 32, pad: [3, 1], type: 'u16', View: Uint16Array },
   mat2x4f: { numElements:  8, align: 16, size: 32,              type: 'f32', View: Float32Array },
   mat2x4h: { numElements:  8, align:  8, size: 16,              type: 'u16', View: Uint16Array },
-  mat3x4f: { numElements: 12, align: 16, size: 48, pad: [3, 1], type: 'f32', View: Float32Array },
-  mat3x4h: { numElements: 12, align:  8, size: 24, pad: [3, 1], type: 'u16', View: Uint16Array },
+  mat3x4f: { numElements: 12, align: 16, size: 48,              type: 'f32', View: Float32Array },
+  mat3x4h: { numElements: 12, align:  8, size: 24,              type: 'u16', View: Uint16Array },
   mat4x4f: { numElements: 16, align: 16, size: 64,              type: 'f32', View: Float32Array },
   mat4x4h: { numElements: 16, align:  8, size: 32,              type: 'u16', View: Uint16Array },