Respect hyphens in helm chart names

From `json2jsii` 0.4.0 onwards, type name sanitization works correctly with kebab case, i.e. it no longer ignores
hyphens, so that names like `ingress-nginx`, which previously have been previously converted to `Ingressnginx`, now get
converted to `IngressNginx`, which is the expected behaviour for kebab case to camel case conversion. However,
`cdk8s-cli`'s helm import has been additionally sanitizing hyphens in chart names, even though hyphens are valid
characters in chart names, so that the change in `json2jsii` had no effect. This patch simplifies the helm importer's
sanitization routine to not remove hyphens anymore, resulting in more correct class names.

src/import/codegen.ts

@@ -256,7 +256,7 @@ export interface HelmObjectDefinition {
 }
 
 export function generateHelmConstruct(typegen: TypeGenerator, def: HelmObjectDefinition) {
-  const noSpecialChars = def.chartName.replace(/([^\w ]|_)/g, '');
+  const noSpecialChars = def.chartName.replace(/([^a-zA-Z0-9- ])/g, '');
   const chartName = TypeGenerator.normalizeTypeName(noSpecialChars);
   const schema = def.schema;
   const repoUrl = def.chartUrl;
@@ -421,4 +421,4 @@ export function generateHelmConstruct(typegen: TypeGenerator, def: HelmObjectDef
 
 function hasRequiredProps(schema: JSONSchema4):boolean | undefined {
   return schema?.required && Array.isArray(schema.required) && schema.required.length > 0;
-}
+}