docs: improve language in types-and-values section (#2874)

I asked Gemini to review the English for inconsistencies and grammar
mistakes. This is the result and I hope it's useful!

As a non-native speaker, it is hard for me to evaluate the finer
details, so let me know if you would like to see changes (or even
better: make them directly in the PR with the suggestion function).

---------

Co-authored-by: Dmitri Gribenko <gribozavr@gmail.com>

src/types-and-values/exercise.md

@@ -4,10 +4,10 @@ minutes: 15
 
 # Exercise: Fibonacci
 
-The Fibonacci sequence begins with `[0,1]`. For n>1, the n'th Fibonacci number
-is calculated recursively as the sum of the n-1'th and n-2'th Fibonacci numbers.
+The Fibonacci sequence begins with `[0, 1]`. For `n > 1`, the next number is the
+sum of the previous two.
 
-Write a function `fib(n)` that calculates the n'th Fibonacci number. When will
+Write a function `fib(n)` that calculates the nth Fibonacci number. When will
 this function panic?
 
 ```rust,editable,should_panic

src/types-and-values/hello-world.md

@@ -32,7 +32,7 @@ Key points:
 - Rust is very much like other languages in the C/C++/Java tradition. It is
   imperative and it doesn't try to reinvent things unless absolutely necessary.
 
-- Rust is modern with full support for things like Unicode.
+- Rust is modern with full support for Unicode.
 
 - Rust uses macros for situations where you want to have a variable number of
   arguments (no function [overloading](../control-flow-basics/functions.md)).

src/types-and-values/values.md

@@ -24,7 +24,7 @@ The types have widths as follows:
 
 <details>
 
-There are a few syntaxes which are not shown above:
+There are a few syntaxes that are not shown above:
 
 - All underscores in numbers can be left out, they are for legibility only. So
   `1_000` can be written as `1000` (or `10_00`), and `123_i64` can be written as