Fixed a couple of exercise references as they are no longer accurate after the recent changes

- Exercise 107 claimed the async exercises are 84-91, they are actually 85-94 and quiz 95
- Exercise 113 claimed the bit manip exercise is 097, it is now 100
- Exercise 114 has the bit manipulation exercises as 097 and 098, they are now 100 and 101
- Exercise 114 has the last switch exercise as being 108, it is now 111.

exercises/107_threading.zig

@@ -1,5 +1,5 @@
 //
-// In Exercises 84-91, we learned about Zig's Io interface for
+// In Exercises 85-94, we learned about Zig's Io interface for
 // concurrent execution: io.async(), Group, Select, and Futures.
 // Under the hood, the Threaded backend manages a pool of real
 // OS threads for you - including scheduling, cancellation, and

exercises/113_quiz9.zig

@@ -14,7 +14,7 @@
 //
 // A common activity in microcontroller programming is setting and clearing
 // bits on input and output pins. This lets you control LEDs, sensors, motors
-// and more! In a previous exercise (097_bit_manipulation.zig) you learned how
+// and more! In a previous exercise (100_bit_manipulation.zig) you learned how
 // to swap two bytes using the ^ (XOR - exclusive or) operator. This quiz will
 // test your knowledge of bit manipulation in Zig while giving you a taste of
 // what it's like to control registers in a real microcontroller. Included at

exercises/114_packed.zig

@@ -1,6 +1,6 @@
 //
 // We've already learned plenty about bit manipulation using bitwise operations
-// in exercises 097 and 098 and in quiz 110. The techniques we already know work
+// in exercises 100 and 101 and in quiz 113. The techniques we already know work
 // just fine, but creating masks and shifting individual bits around can become
 // quite tedious and unwieldy pretty quickly.
 // What if there was a better, a more convenient way to control individual bits?

exercises/115_packed2.zig

@@ -1,5 +1,5 @@
 //
-// We've already learned about switch statements in exercises 030, 031 and 108.
+// We've already learned about switch statements in exercises 030, 031 and 111.
 // They also work with packed containers:
 
 const S = packed struct(u2) {