pseudorandom.ts minor fixes (#2046)

## Description:

in src/core/pseudorandom.ts
a helper function of nextint is defined but never used. 
instead, this.rng is used. those are replaced.

also, shuffleArray originally would self-shuffle at i=0 for the
conditional being i>=0, fixed to 0.

## Please complete the following:

- [X] I have added screenshots for all UI updates
- [X] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [X] I have added relevant tests to the test directory
- [X] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

jack_45183

src/core/PseudoRandom.ts

@@ -36,7 +36,7 @@ export class PseudoRandom {
     if (arr.length === 0) {
       throw new Error("array must not be empty");
     }
-    return arr[Math.floor(this.rng() * arr.length)];
+    return arr[this.nextInt(0, arr.length)];
   }
 
   // Selects a random element from a set.
@@ -61,14 +61,14 @@ export class PseudoRandom {
 
   // Returns true with probability 1/odds.
   chance(odds: number): boolean {
-    return Math.floor(this.rng() * odds) === 0;
+    return this.nextInt(0, odds) === 0;
   }
 
   // Returns a shuffled copy of the array using Fisher-Yates algorithm.
   shuffleArray<T>(array: T[]): T[] {
     const result = [...array];
-    for (let i = result.length - 1; i >= 0; i--) {
-      const j = Math.floor(this.rng() * (i + 1));
+    for (let i = result.length - 1; i > 0; i--) {
+      const j = this.nextInt(0, i + 1);
       [result[i], result[j]] = [result[j], result[i]];
     }
     return result;