Merge bitcoin/bitcoin#22420: doc: Specifiy how to set the value of TORGROUP

5984084 Specifies how to set the value of TORGROUP (lsilva01)

Pull request description:

  This change just makes it more explicit how to assign the value to the TORGROUP variable.

ACKs for top commit:
  laanwj:
    ACK 5984084
  Zero-1729:
    Concept ACK 5984084

Tree-SHA512: af5cc0f87fa309201b5937a2741dea9374eafc09e84664ca138669c1827ce44fe6d25e3853d53ed2c838321aa4b28c6fd9d8dbe23f7194fdd6559d49453416e4

Author: laanwj

doc/tor.md

@@ -133,7 +133,7 @@ You can also check the group of the cookie file. On most Linux systems, the Tor
 auth cookie will usually be `/run/tor/control.authcookie`:
 
 ```
-stat -c '%G' /run/tor/control.authcookie
+TORGROUP=$(stat -c '%G' /run/tor/control.authcookie)
 ```
 
 Once you have determined the `${TORGROUP}` and selected the `${USER}` that will