root-src: remove weasel words (#3039)

This PR removes imprecise language ('weasel words') to align with the
new precision guidelines in #3029.

---
*Note: This PR was generated using Gemini. Please review the changes
accordingly. If the new style is not desired for this section, feel free
to close this PR.*

Author: mgeisler

src/thanks.md

@@ -7,8 +7,8 @@ course: none
 _Thank you for taking Comprehensive Rust 🦀!_ We hope you enjoyed it and that it
 was useful.
 
-We've had a lot of fun putting the course together. The course is not perfect,
-so if you spotted any mistakes or have ideas for improvements, please get in
+We have enjoyed putting the course together. The course is not perfect, so if
+you spotted any mistakes or have ideas for improvements, please get in
 [contact with us on GitHub](https://github.com/google/comprehensive-rust/discussions).
 We would love to hear from you.
 

src/welcome-day-1.md

@@ -7,7 +7,8 @@ target_minutes: 180
 
 # Welcome to Day 1
 
-This is the first day of Rust Fundamentals. We will cover a lot of ground today:
+This is the first day of Rust Fundamentals. We will cover a broad range of
+topics today:
 
 - Basic Rust syntax: variables, scalar and compound types, enums, structs,
   references, functions, and methods.