Update dependency macos to v26

Author: renovate[bot]

.github/workflows/ci.yml

@@ -1028,7 +1028,7 @@ jobs:
 
   bazel_osx:
     name: Bazel on MacOS
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
     - name: Harden the runner (Audit all outbound calls)
       uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3

.github/workflows/cmake_install.yml

@@ -292,7 +292,7 @@ jobs:
 
   macos_conan_stable:
     name: macOS conan stable versions cxx17 (static libs)
-    runs-on: macos-15
+    runs-on: macos-26
     env:
       INSTALL_TEST_DIR: '/Users/runner/install_test'
       CXX_STANDARD: '17'
@@ -329,7 +329,7 @@ jobs:
 
   macos_brew_packages:
     name: macOS brew latest versions cxx17 (static libs)
-    runs-on: macos-15
+    runs-on: macos-26
     env:
       INSTALL_TEST_DIR: '/Users/runner/install_test'
       CXX_STANDARD: '17'