add 1.15.2 release notes (#1073)

Author: kevinAlbs

CHANGELOG.md

@@ -10,6 +10,11 @@
   - This applies to IntelDFP when `MONGOCRYPT_DFP_DIR` is not set to `USE-SYSTEM`.
   - Note: `FetchContent_Populate()` is still used for CMake versions prior to 3.18 to avoid `add_subdirectory()` behavior.
 
+## 1.15.2
+
+### Fixed
+- Rename internal headers to avoid conflicts building libmongocrypt and C driver together.
+
 ## 1.15.1
 
 ### Fixed