doc: simplify text in pull-requests.md

Mostly, this replaces "It is recommended to do X" with "Do X."

PR-URL: #30458
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

doc/guides/contributing/pull-requests.md

@@ -73,7 +73,7 @@ $ git remote add upstream https://github.com/nodejs/node.git
 $ git fetch upstream
 ```
 
-It is recommended to configure `git` so that it knows who you are:
+Configure `git` so that it knows who you are:
 
 ```text
 $ git config user.name "J. Random User"
@@ -125,7 +125,7 @@ For contributing C++ code, you may want to look at the
 
 ### Step 4: Commit
 
-It is a recommended best practice to keep your changes as logically grouped
+It is a best practice to keep your changes as logically grouped
 as possible within individual commits. There is no limit to the number of
 commits any single Pull Request may have, and many contributors find it easier
 to review changes that are split across multiple commits.