It probably fails with:

Unexpected reserved word 'await'.

and that's because await keyword could be used only in async functions, your callback function is not async.

You might write:

it("show something", async () => {
  await cy.wait("@firstApiCall");
  await cy.wait("@firstApiCall");

  cy.get("test:something").should("exist");
});

But I wonder why do you want to do it? Cypress does a good job running the commands in the order in which they are written (https://docs.cypress.io/guides/core-concepts/introduction-to-cypress#Commands-Run-Serially).

I also doubt your example actually works:

describe("some page", () => {
  beforeEach(() => {
    cy.intercept("/users", {
      fixture: users.json,
    });
    cy.visit("/somewhere");
  });

  it("show something", () => {
    cy.wait("@firstApiCall").then(() => {
      cy.wait("@2ndApiCall").then(() => {
        cy.get("test:something").should("exist");
      });
    });
  });
});

You don't alias firstApiCall and 2ndApiCall, so Cypress doesn't know what to wait for.