doc: use the same case as the section heading

Refs: https://github.com/nodejs/node#verifying-binaries

PR-URL: nodejs#41876
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

README.md

@@ -704,7 +704,7 @@ gpg --keyserver pool.sks-keyservers.net --recv-keys 108F52B48DB57BB0CC439B2997B0
 gpg --keyserver pool.sks-keyservers.net --recv-keys B9E2F5981AA6E0CD28160D9FF13993A75599653C
 ```
 
-See the section above on [Verifying Binaries](#verifying-binaries) for how to
+See the section above on [Verifying binaries](#verifying-binaries) for how to
 use these keys to verify a downloaded file.
 
 <details>