openapi-framework: fix typing operations (allow array)

Hello, small change to the typing of the operations attribute in order for it to be aligned with the changes in https://github.com/kogosoftwarellc/open-api/pull/769.

No breaking change as it simply adds the array as an additional type.

Thank you 🙂

[x] I only have 1 commit.
[x] My commit is prefixed with the relevant package (e.g. express-openapi: fixing something) Note: You can use the bin/commit script to automate this.
[x] I have added tests. (well it's only typing...)
[x] I'm using the latest code from the master branch and there are no conflicts on my branch.
[x] I have added a suffix to my commit message that will close any existing issue my PR addresses.
[x] My tests pass locally.
[x] I have run linting against my code.

kogosoftwarellc / open-api