FetchContent: Bump documented example Catch2 to v3.0.1
This addresses a minor issue: I tried https://cmake.org/cmake/help/v3.26/module/FetchContent.html#typical-case, but v2.13.4 does not compile by GCC 12 or Clang 15 on EndeavourOS (https://github.com/catchorg/Catch2/issues/2326).
Backport: release
Topic-rename: doc-FetchContent-catch2
Edited by Brad King