[libcxx][docs][dfsan] Fix rst rendering related typos

[zbrid]

Summary

• Fix the code block disappearance problem by adding a new line
• Fix the typo where I forgot a space

clang/docs/DataFlowSanitizer.rst

 specific class of bugs on its own.  Instead, it provides a generic
 dynamic data flow analysis framework to be used by clients to help
 detect application-specific issues within their own code.
 
 How to build libc++ with DFSan
 ==============================
 
 DFSan requires either all of your code to be instrumented or for uninstrumented
-functions to be listed as``uninstrumented`` in the `ABI list`_.
+functions to be listed as ``uninstrumented`` in the `ABI list`_.
 
 If you'd like to have instrumented libc++ functions, then you need to build it
 with DFSan instrumentation from source. Here is an example of how to build
 libc++ and the libc++ ABI with data flow sanitizer instrumentation.
 
 .. code-block:: console
+
   cd libcxx-build
 
   # An example using ninja
   cmake -GNinja path/to/llvm-project/llvm \
     -DCMAKE_C_COMPILER=clang \
     -DCMAKE_CXX_COMPILER=clang++ \
     -DLLVM_USE_SANITIZER="DataFlow" \
     -DLLVM_ENABLE_LIBCXX=ON \