[mod] default-output-fn: omit "?" location info

Change intended to reduce unhelpful noise in output

Before this commit:
  2024-08-30T07:34:40.806Z MyHostName INFO [my.ns:126] - My message ; Have ns, line
  2024-08-30T07:34:40.806Z MyHostName INFO [my.ns:?] - My message   ; Have ns only
  2024-08-30T07:34:40.806Z MyHostName INFO [?:?] - My message       ; Have neither

After this commit:
  2024-08-30T07:34:40.806Z MyHostName INFO [my.ns:126] - My message ; Have ns, line (unchanged)
  2024-08-30T07:34:40.806Z MyHostName INFO [my.ns] - My message     ; Have ns only  (omit "?")
  2024-08-30T07:34:40.806Z MyHostName INFO - My message             ; Have neither  (omit "[?:?]")

src/taoensso/timbre.cljc

@@ -837,7 +837,10 @@
        (when-let [ts (force timestamp_)] (str ts " "))
        #?(:clj (force hostname_))  #?(:clj " ")
        (str/upper-case (name level))  " "
-       "[" (or ?ns-str ?file "?") ":" (or ?line "?") "] - "
+       ;; "[" (or ?ns-str ?file "?") ":" (or ?line "?") "] - "
+       (when-let [loc (or ?ns-str ?file)]
+         (str "[" loc (when-let [line ?line] (str ":" line)) "]"))
+       " - "
 
        (when-let [msg-fn (get output-opts :msg-fn default-output-msg-fn)]
          (msg-fn data))