Add warnings example in v2.3 migration guide (#5627)

website/docs/usage/v2-3.md

@@ -161,10 +161,18 @@ debugging your tokenizer configuration.
 
 spaCy's custom warnings have been replaced with native Python
 [`warnings`](https://docs.python.org/3/library/warnings.html). Instead of
-setting `SPACY_WARNING_IGNORE`, use the
-[`warnings` filters](https://docs.python.org/3/library/warnings.html#the-warnings-filter)
+setting `SPACY_WARNING_IGNORE`, use the [`warnings`
+filters](https://docs.python.org/3/library/warnings.html#the-warnings-filter)
 to manage warnings.
 
+```diff
+import spacy
++ import warnings
+
+- spacy.errors.SPACY_WARNING_IGNORE.append('W007')
++ warnings.filterwarnings("ignore", message=r"\[W007\]", category=UserWarning)
+```
+
 #### Normalization tables
 
 The normalization tables have moved from the language data in