corrected default versioning and fixed build error

Author: riseandshaheen

docusaurus.config.js

@@ -185,7 +185,7 @@ const config = {
           },
           {
             label: "Rollups",
-            to: "/cartesi-rollups/2.0",
+            to: "/cartesi-rollups/1.5",
             activeBaseRegex: "^/cartesi-rollups",
             position: "left",
           },
@@ -365,9 +365,9 @@ const config = {
           ],
         },
         versions: {
-          "2.0": {
-            label: "2.0",
-            path: "2.0",
+          "1.5": {
+            label: "1.5",
+            path: "1.5",
           },
         },
         showLastUpdateTime: true,
@@ -379,7 +379,7 @@ const config = {
         redirects: [
           {
             from: '/cartesi-rollups',      // the old/base route
-            to:   '/cartesi-rollups/2.0/', // the new route to redirect to
+            to:   '/cartesi-rollups/1.5/', // the new route to redirect to
           },
         ],
       },