NaCl docs: fix a few more issues with the ARM sandbox documentation.

native_client_sdk/src/doc/reference/sandbox_internals/index.rst

Index: native_client_sdk/src/doc/reference/sandbox_internals/index.rst
diff --git a/native_client_sdk/src/doc/reference/sandbox_internals/index.rst b/native_client_sdk/src/doc/reference/sandbox_internals/index.rst
index 225c4e77a526c62756f9e066a249eea6cbe20561..3b5670d119e7cc7560ab1dc078c5819ddd4a5c6a 100644
--- a/native_client_sdk/src/doc/reference/sandbox_internals/index.rst
+++ b/native_client_sdk/src/doc/reference/sandbox_internals/index.rst
@@ -4,8 +4,8 @@
 Sandbox Internals
 #################
 
-The sandbox internals explains implementation details about Native
-Client sandboxing, which is also used by Portable Native Client. These
-details can be useful to reimplement a sandbox, or to write assembly
-code that follows sandboxing rules for Native Client (Portable Native
-Client doesn't allow developers to write platform-specific assembly).
+The sandbox internals documentation describes implementation details for
+Native Client sandboxing, which is also used by Portable Native
+Client. These details can be useful to reimplement a sandbox, or to
+write assembly code that follows sandboxing rules for Native Client
+(Portable Native Client does not allow platform-specific assembly code).