docs: fix typo in process column config (#1323)

Lowercase a word.

docs/content/configuration/config-file/processes.md

@@ -7,5 +7,5 @@ You can configure which columns are shown by the process widget by setting the `
 ```toml
 [processes]
 # Pick which columns you want to use in any order.
-columns = ["cpu%", "mem%", "pid", "name", "read", "write", "Tread", "twrite", "state", "user", "time"]
+columns = ["cpu%", "mem%", "pid", "name", "read", "write", "tread", "twrite", "state", "user", "time"]
 ```