Fix misleading placeholder when creating a new Alerting Integration Contact Point (#4327)

# What this PR does
It was not clear that the user was expected to enter a name for the new
contact point. Changed "Choose Contact Point" to "Enter New Contact
Point Name"
<img width="625" alt="Screenshot 2024-05-09 at 3 42 50 PM"
src="https://github.com/grafana/oncall/assets/2262529/dd2ba427-d009-4858-a509-3c46d349eb60">


## Which issue(s) this PR closes

Closes [issue link here]

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## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

Co-authored-by: Joey Orlando <joey.orlando@grafana.com>

grafana-plugin/src/components/IntegrationContactPoint/IntegrationContactPoint.tsx

@@ -225,7 +225,7 @@ export const IntegrationContactPoint: React.FC<{
         ) : (
           <Input
             value={selectedContactPoint}
-            placeholder="Choose Contact Point"
+            placeholder="Enter New Contact Point Name"
             onChange={({ target }) => {
               const value = (target as HTMLInputElement).value;
               setState({ selectedContactPoint: value });