Tweak message about GIT_PYTHON_REFRESH for 80-column terminals

The fragment of the refresh failure message (which is often written
to a terminal) about the effect of setting GIT_PYTHON_REFRESH to
control refesh failure reporting had previously been formatted with
a maximum line length of 79 columns--in the message itself, not the
code for the message--so that it would fit in a traditional 80
column wide terminal. This remains one of the popular widths to set
for terminal windows in a GUI, so it seems worthwhile to preserve.

In 3a6e3ef (gitpython-developers#1815), I had inadvertently made the line one character
too long for that; at 80 columns, it would cause the newline to be
written at the start of the next line, creating an unsightly extra
line break.

This is pretty minor, but what seems to me like an equally good
alternative wording avoids it, so this commit shortens the wording.

git/cmd.py

@@ -479,7 +479,7 @@ def refresh(cls, path: Union[None, PathLike] = None) -> bool:
                         This initial message can be silenced or aggravated in the future by setting the
                         $%s environment variable. Use one of the following values:
                             - %s: for no message or exception
-                            - %s: for a warning message (logged at level CRITICAL, displayed by default)
+                            - %s: for a warning message (logging level CRITICAL, displayed by default)
                             - %s: for a raised exception
 
                         Example:
@@ -509,7 +509,7 @@ def refresh(cls, path: Union[None, PathLike] = None) -> bool:
 
                         Use only the following values:
                             - %s: for no message or exception
-                            - %s: for a warning message (logged at level CRITICAL, displayed by default)
+                            - %s: for a warning message (logging level CRITICAL, displayed by default)
                             - %s: for a raised exception
                         """
                         )