no-system-props: allow maxWidth prop for Truncate (#149)

* add maxWidth to allow list for Truncate

* Create lazy-planes-prove.md

Author: siddharthkp

.changeset/lazy-planes-prove.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-primer-react": patch
+---
+
+no-system-props: allow maxWidth prop for Truncate

src/rules/no-system-props.js

@@ -42,6 +42,7 @@ const excludedComponentProps = new Map([
   ['PageLayout.Content', new Set(['padding', 'width'])],
   ['ProgressBar', new Set(['bg'])],
   ['PointerBox', new Set(['bg'])],
+  ['Truncate', new Set(['maxWidth'])],
 ])
 
 const alwaysExcludedProps = new Set(['variant', 'size'])