Open dictionary files always using O_RDONLY.

We never directly write to opened and mmapped files.

Bug: 11391620

Change-Id: Ic52fbe6018b8b3c1b6ca687461f29185809217c2
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.cpp
index 71f8632..28af973 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.cpp
@@ -30,8 +30,7 @@
 /* static */ MmappedBuffer::MmappedBufferPtr MmappedBuffer::openBuffer(
         const char *const path, const int bufferOffset, const int bufferSize,
         const bool isUpdatable) {
-    const int openMode = isUpdatable ? O_RDWR : O_RDONLY;
-    const int mmapFd = open(path, openMode);
+    const int mmapFd = open(path, O_RDONLY);
     if (mmapFd < 0) {
         AKLOGE("DICT: Can't open the source. path=%s errno=%d", path, errno);
         return MmappedBufferPtr(0);