Merge #1759: ci: Switch to macOS 15 Sequoia Intel-based image

8bc50b7 ci: Switch to macOS 15 Sequoia Intel-based image (Hennadii Stepanov)

Pull request description:

  This is an alternative to #1755.

  More details from the GHA developers:
  > Apple has discontinued support for the x86_64 (Intel) architecture going forward. GitHub will no longer support this architecture on macOS after the macOS 15 runner image is retired in Fall 2027.

ACKs for top commit:
  real-or-random:
    ACK 8bc50b7

Tree-SHA512: 2c3de907b8910193b77bb201e1c7aad3f70f89804efe4b3ead23181d45a912f677cd533e819914cf1b346aa01d2f273fd5f1e63d7b8d284320d1e4e6198d8578

Author: real-or-random

.github/workflows/ci.yml

@@ -429,9 +429,8 @@ jobs:
       - *PRINT_LOGS
 
   x86_64-macos-native:
-    name: "x86_64: macOS Ventura, Valgrind"
-    # See: https://github.com/actions/runner-images#available-images.
-    runs-on: macos-13
+    name: "x86_64: macOS Sequoia, Valgrind"
+    runs-on: macos-15-intel
 
     env:
       CC: 'clang'