Remove underscores from integer literals in swagger.yaml.

With:
```
$ yq --version
yq (https://github.com/mikefarah/yq/) version v4.40.5
```

Before applying this commit:
```
$ yq eval specifications/api/swagger.yaml -o=json
Error: json: error calling MarshalJSON for type *yqlib.CandidateNode:
json: error calling MarshalJSON for type *yqlib.CandidateNode: json:
error calling MarshalJSON for type *yqlib.CandidateNode:
strconv.ParseInt: parsing "45_000_000_000_000_000": invalid syntax
```

After applying this commit, the error disappears.

specifications/api/swagger.yaml

@@ -4111,7 +4111,7 @@ x-parametersIntendedStakeAmount: &parametersIntendedStakeAmount
   schema:
     type: integer
     minimum: 0
-    maximum: 45_000_000_000_000_000 # 45 B ada (in Lovelace)
+    maximum: 45000000000000000 # 45 B ada (in Lovelace)
   description: |
     The stake the user intends to delegate in Lovelace. Required.