Change shebangs to the more portable /usr/bin/env bash

This resolves issues on systems where bash is not in /bin/bash (e.g.
NixOS).

Bin/system-stats.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # A Bash script to monitor system stats and output them in JSON format.
 # This script is a conversion of ZigStat
@@ -199,4 +199,4 @@ while true; do
 
   # Wait for the specified duration before the next update.
   sleep "$SLEEP_DURATION"
-done
+done

Bin/test-notifications.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 echo "Sending 8 test notifications..."
 
@@ -8,4 +8,4 @@ for i in {1..8}; do
     sleep 1
 done
 
-echo "All notifications sent!" 
+echo "All notifications sent!"