[llvm][docs] Fix indentation of item list. [NFCI]

[fpetrogalli]

Summary

This fixes the rendering of the items at https://llvm.org/docs/GettingStarted.html#stand-alone-builds

[tstellar]

LGTM.

llvm/docs/GettingStarted.rst

cmake -G Ninja -S path/to/llvm-project/$subproj \
         -DLLVM_ROOT=/path/to/llvm/install/prefix
 
 Notice that:
 
 * The stand-alone build needs to happen in a folder that is not the
   original folder where LLVMN was built
   (`$builddir!=$builddir_subproj`).
 * ``LLVM_ROOT`` should point to the prefix of your llvm installation,
-   so for example, if llvm is installed into ``/usr/bin`` and
-   ``/usr/lib64``, then you should pass ``-DLLVM_ROOT=/usr/``.
 * Both the ``LLVM_ROOT`` and ``LLVM_EXTERNAL_LIT`` options are
   required to do stand-alone builds for all sub-projects.  Additional
   required options for each sub-project can be found in the table
   below.
 
 The ``check-$subproj`` and ``install`` build targets are supported for the
 sub-projects listed in the table below.