Remove unnecessary sensationalism in docs

SQL injection and failures are bad but this seems over the top. In a
literal sense I'm struggling to imagine a scenario where bad
interpolation is worth getting shot over. And I understand this was
probably intended as hyperbole, but I don't think there's any need to
invoke the spectre of violence to make the point here.

doc/src/usage.rst

@@ -211,7 +211,7 @@ reliable. We must stress this point:
 
     Never, **never**, **NEVER** use Python string concatenation (``+``) or
     string parameters interpolation (``%``) to pass variables to a SQL query
-    string.  Not even at gunpoint.
+    string.
 
 The correct way to pass variables in a SQL command is using the second
 argument of the `~cursor.execute()` method::