refactor(ec2): rename getImage parameter (#35119)

### Reason for this change

The parameter name `_` caused jsii processing issues for Java versions newer than version 9. This is because `_` is a preserved keyword there.

### Description of changes

Renamed parameter from `_` to `_scope` instead.

### Describe any new or updated permissions being added

No new permissions are added.

### Description of how you validated changes

N/A

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: Abogical

packages/aws-cdk-lib/aws-ec2/lib/machine-image/machine-image.ts

@@ -252,7 +252,7 @@ export class ResolveSsmParameterAtLaunchImage implements IMachineImage {
   /**
    * Return the image to use in the given context
    */
-  public getImage(_: Construct): MachineImageConfig {
+  public getImage(_scope: Construct): MachineImageConfig {
     const versionString = this.props.parameterVersion ? `:${this.props.parameterVersion}` : '';
     const osType = this.props.os ?? OperatingSystemType.LINUX;
     return {