docs: don't recommend verbose logs for nodes

We crank up verbosity on our PL nodes and validators, because we want
maximum visibility into application state. We don't need to recommend
that everyone running a node does the same, given that log volume is
clocking in around 20GB/week per pd instance running in a testnet.

docs/guide/src/dev/devnet-quickstart.md

@@ -17,9 +17,10 @@ This will write configs to `~/.penumbra/testnet_data/`.
 
 ## Running `pd`
 
-You'll probably want to set `RUST_LOG`.  Here's one suggestion:
+You'll probably want to set `RUST_LOG`.  Here's one suggestion that's quite verbose:
 
 ```shell
+# Optional. Expect about 20GB/week of log data for pd with settings below.
 export RUST_LOG="info,pd=debug,penumbra=debug,jmt=debug"
 ```
 

docs/guide/src/pd/join-testnet.md

@@ -50,12 +50,7 @@ the section above on resetting node state.
 ### Running `pd` and `tendermint`
 
 Next, run `pd` with the `--home` parameter pointed at the correct part of the
-testnet data directory.  It's useful to set the `RUST_LOG` environment variable
-to get information about what it's doing:
-
-```shell
-export RUST_LOG="info,pd=debug,penumbra=debug,jmt=debug" # or some other logging level
-```
+testnet data directory.
 
 ```shell
 cargo run --bin pd --release -- start --home ~/.penumbra/testnet_data/node0/pd