std: remove logging example (#8877)

The example is is going to be included in the documentation, so I think
we no longer need it here.
See: https://github.com/nushell/nushell.github.io/pull/870

crates/nu-std/examples.nu

@@ -1,13 +0,0 @@
-use std 'log debug'
-use std 'log info'
-use std 'log warning'
-use std 'log error'
-use std 'log critical'
-
-export def log [] {
-    log debug "Debug message"
-    log info "Info message"
-    log warning "Warning message"
-    log error "Error message"
-    log critical "Critical message"
-}