Fixed linting errors

[kirex0]

Public API Changes
None

Description
This PR fixes an issue with the linter during the build process. The following errors are thrown when trying to build this package.

/usr/local/share/.cache/yarn/v6/.tmp/daaec974064c5e8d044980d3e6858ff6.f25904a999239d9a8bb4e70561e27643b468a71d.prepare/src/urdf/UrdfBox.ts
  23:9  error  Prefer using an optional chain expression instead, as it's more concise and easier to read  @typescript-eslint/prefer-optional-chain
/usr/local/share/.cache/yarn/v6/.tmp/daaec974064c5e8d044980d3e6858ff6.f25904a999239d9a8bb4e70561e27643b468a71d.prepare/src/urdf/UrdfColor.ts
  35:9  error  Prefer using an optional chain expression instead, as it's more concise and easier to read  @typescript-eslint/prefer-optional-chain
/usr/local/share/.cache/yarn/v6/.tmp/daaec974064c5e8d044980d3e6858ff6.f25904a999239d9a8bb4e70561e27643b468a71d.prepare/src/urdf/UrdfMesh.ts
  29:9  error  Prefer using an optional chain expression instead, as it's more concise and easier to read  @typescript-eslint/prefer-optional-chain
/usr/local/share/.cache/yarn/v6/.tmp/daaec974064c5e8d044980d3e6858ff6.f25904a999239d9a8bb4e70561e27643b468a71d.prepare/src/urdf/UrdfUtils.ts
  10:7  error  Prefer using an optional chain expression instead, as it's more concise and easier to read  @typescript-eslint/prefer-optional-chain
  21:7  error  Prefer using an optional chain expression instead, as it's more concise and easier to read  @typescript-eslint/prefer-optional-chain