doc: remove shell dollar signs without output

Related to https://github.com/nodejs/remark-preset-lint-node/pull/94

PR-URL: https://github.com/nodejs/node/pull/33692
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

doc/guides/building-node-with-ninja.md

@@ -29,7 +29,7 @@ number of processes to run for [Ninja][] using the environment variable `JOBS`.
 This will be the equivalent to the `-j` parameter in the regular `make`:
 
 ```bash
-$ JOBS=12 make
+JOBS=12 make
 ```
 
 ## Producing a debug build
@@ -37,7 +37,7 @@ $ JOBS=12 make
 To create a debug build rather than a release build:
 
 ```bash
-$ ./configure --ninja --debug && make
+./configure --ninja --debug && make
 ```
 
 [Ninja]: https://ninja-build.org/