chore: Remove unused env variable (#3091)

Seems to be unused


![image](https://github.com/user-attachments/assets/2b32f19c-8a3c-469b-9e17-d735cd36288d)

Author: tjzel

android/build.gradle

@@ -118,8 +118,7 @@ android {
             externalNativeBuild {
                 cmake {
                     cppFlags "-O2", "-frtti", "-fexceptions", "-Wall", "-Werror", "-std=c++20", "-DANDROID"
-                    arguments "-DAPP_BUILD_DIR=${appProject.buildDir}",
-                        "-DREACT_NATIVE_DIR=${REACT_NATIVE_DIR}",
+                    arguments "-DREACT_NATIVE_DIR=${REACT_NATIVE_DIR}",
                         "-DREACT_NATIVE_MINOR_VERSION=${REACT_NATIVE_MINOR_VERSION}",
                         "-DANDROID_STL=c++_shared"
                     abiFilters (*reactNativeArchitectures())