fix: implicit-return-type warning for BaseVersions.setVersions()

Author: ckerr

src/versions.ts

@@ -88,7 +88,7 @@ const NUM_SUPPORTED_MAJORS = 4;
 export class BaseVersions implements Versions {
   private readonly map = new Map<string, SemVer>();
 
-  protected setVersions(val: unknown) {
+  protected setVersions(val: unknown): void {
     // build the array
     let parsed: Array<SemVer | null> = [];
     if (isArrayOfVersionObjects(val)) {