doc: fix links to Style Guide and CPP Style Guide

PR-URL: #18683
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/guides/contributing/pull-requests.md

@@ -109,12 +109,12 @@ If you are modifying code, please be sure to run `make lint` from time to
 time to ensure that the changes follow the Node.js code style guide.
 
 Any documentation you write (including code comments and API documentation)
-should follow the [Style Guide](doc/STYLE_GUIDE.md). Code samples included
+should follow the [Style Guide](../../STYLE_GUIDE.md). Code samples included
 in the API docs will also be checked when running `make lint` (or
 `vcbuild.bat lint` on Windows).
 
 For contributing C++ code, you may want to look at the
-[C++ Style Guide](CPP_STYLE_GUIDE.md).
+[C++ Style Guide](../../../CPP_STYLE_GUIDE.md).
 
 ### Step 4: Commit