Say C++17 everywhere the project describes itselfchore/cpp17-descriptions

The move to C++17 left a trail of older claims. The Runner's own
.clang-format still said c++20; the result is byte for byte the same under
either value. Premake and Xmake still compiled the library as C++20 and
the main library as C++14, which meant their CI jobs were not testing the
language the project promises. Both now use C++17 for every target.

The rest is text: the Meson pkg-config description claimed C++14, comments
in the CMake and Meson files explained requirements that no longer exist,
.clang-tidy gave C++14 as the reason for two exclusions, issue templates
asked for C++20 samples, and the example headers named -std=c++14 and
catch2-with-main. The release notes and the migration guide state the
C++17 minimum. Doxygen's brief called the project "Catch2's test API",
which presents it as Catch2. Meson declared only BSL-1.0; it now names both
licenses of the tree. The amalgamated files are regenerated.

1 files changed, 1 insertions, 1 deletions

diff --git a/.github/ISSUE_TEMPLATE/bug_report.md b/.github/ISSUE_TEMPLATE/bug_report.md
index 7d640168..81c651c9 100644
--- a/.github/ISSUE_TEMPLATE/bug_report.md
+++ b/.github/ISSUE_TEMPLATE/bug_report.md
@@ -26,7 +26,7 @@ Describe the expected behavior and the contract or documentation that supports i
 
 ### Minimal reproduction
 
-Provide a small C++20 test, the command used to build and run it, and the test-runner arguments. For a property failure, include the root seed, replay seed, trial number, and minimized counterexample when available. For a snapshot failure, describe the snapshot mode and file location without pasting private content.
+Provide a small C++17 test, the command used to build and run it, and the test-runner arguments. For a property failure, include the root seed, replay seed, trial number, and minimized counterexample when available. For a snapshot failure, describe the snapshot mode and file location without pasting private content.
 
 ### Environment