[ci] upgrade to GoogleTest v1.14.0 (fixes #5976) (#5981)

CMakeLists.txt

@@ -41,6 +41,13 @@ endif()
 
 project(lightgbm LANGUAGES C CXX)
 
+if(BUILD_CPP_TEST)
+  set(CMAKE_CXX_STANDARD 14)
+else()
+  set(CMAKE_CXX_STANDARD 11)
+endif()
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
 list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake/modules")
 
 #-- Sanitizer
@@ -329,7 +336,7 @@ endif()
 if(UNIX OR MINGW OR CYGWIN)
   set(
     CMAKE_CXX_FLAGS
-    "${CMAKE_CXX_FLAGS} -std=c++11 -pthread -Wextra -Wall -Wno-ignored-attributes -Wno-unknown-pragmas -Wno-return-type"
+    "${CMAKE_CXX_FLAGS} -pthread -Wextra -Wall -Wno-ignored-attributes -Wno-unknown-pragmas -Wno-return-type"
   )
   if(MINGW)
     # ignore this warning: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95353
@@ -630,7 +637,7 @@ if(BUILD_CPP_TEST)
     FetchContent_Declare(
       googletest
       GIT_REPOSITORY https://github.com/google/googletest.git
-      GIT_TAG        release-1.11.0
+      GIT_TAG        v1.14.0
     )
     FetchContent_MakeAvailable(googletest)
     add_library(GTest::GTest ALIAS gtest)