Fix f-string docs mistake (#349)

Author: alexmojaki

docs/guides/onboarding_checklist/add_manual_tracing.md

@@ -145,8 +145,8 @@ Contrary to the previous section, this _will_ work well in Python 3.11+ because
 
 - The feature is enabled by default in Python 3.11+. You can disable it with [`logfire.configure(inspect_arguments=False)`][logfire.configure(inspect_arguments)]. You can also enable it in Python 3.9 and 3.10, but it's more likely to not work correctly.
 - Inspecting arguments is expected to always work under normal circumstances. The main caveat is that the source code must be available, so e.g. deploying only `.pyc` files will cause it to fail.
-- If inspecting arguments fails, you will get a warning, and the f-string argument will be treated as a normal string. This means you will get high-cardinality span names such as `'Hello Alice'` and no `name` attribute, but the information won't be completely lost.
-- If inspecting arguments is enabled, then arguments will be inspected regardless of whether f-strings are being used. So if you write `logfire.info('Hello {name}', name=name)` and inspecting arguments fails, then you will still get a warning and `'Hello {name}'` will be used as the message rather than formatting it.
+- If inspecting arguments fails, you will get a warning, and the f-string argument will be used as a formatting template. This means you will get high-cardinality span names such as `'Hello Alice'` and no `name` attribute, but the information won't be completely lost.
+- If inspecting arguments is enabled, then arguments will be inspected regardless of whether f-strings are being used. So if you write `logfire.info('Hello {name}', name=name)` and inspecting arguments fails, then you will still get a warning.
 - The values inside f-strings are evaluated and formatted by Logfire a second time. This means you should avoid code like `logfire.info(f'Hello {get_username()}')` if `get_username()` (or the string conversion of whatever it returns) is expensive or has side effects.
 - The first argument must be an actual f-string. `logfire.info(f'Hello {name}')` will work, but `message = f'Hello {name}'; logfire.info(message)` will not, nor will `logfire.info('Hello ' + name)`.
 - Inspecting arguments is cached so that the performance overhead of repeatedly inspecting the same f-string is minimal. However, there is a non-negligible overhead of parsing a large source file the first time arguments need to be inspected inside it. Either way, avoiding this overhead requires disabling inspecting arguments entirely, not merely avoiding f-strings.