fix(templates): remove main entry points for Vue and React

CodeSandbox doesn't compile bundles correctly with these two frameworks when the `main` entry point is specified.

Author: francoischalifour

e2e/__snapshots__/templates.test.js.snap

@@ -4301,7 +4301,6 @@ exports[`Templates React InstantSearch File content: package.json 1`] = `
   \\"name\\": \\"react-instantsearch-app\\",
   \\"version\\": \\"1.0.0\\",
   \\"private\\": true,
-  \\"main\\": \\"src/App.js\\",
   \\"scripts\\": {
     \\"start\\": \\"react-scripts start\\",
     \\"build\\": \\"react-scripts build\\",
@@ -4956,7 +4955,6 @@ exports[`Templates Vue InstantSearch 1 File content: package.json 1`] = `
   \\"name\\": \\"vue-instantsearch-app\\",
   \\"version\\": \\"1.0.0\\",
   \\"private\\": true,
-  \\"main\\": \\"src/App.vue\\",
   \\"scripts\\": {
     \\"start\\": \\"vue-cli-service serve --port 3000\\",
     \\"build\\": \\"vue-cli-service build\\",
@@ -5279,7 +5277,6 @@ exports[`Templates Vue InstantSearch File content: package.json 1`] = `
   \\"name\\": \\"vue-instantsearch-app\\",
   \\"version\\": \\"1.0.0\\",
   \\"private\\": true,
-  \\"main\\": \\"src/App.vue\\",
   \\"scripts\\": {
     \\"start\\": \\"vue-cli-service serve --port 3000\\",
     \\"build\\": \\"vue-cli-service build\\",

src/templates/React InstantSearch/package.json

@@ -2,7 +2,6 @@
   "name": "{{name}}",
   "version": "1.0.0",
   "private": true,
-  "main": "src/App.js",
   "scripts": {
     "start": "react-scripts start",
     "build": "react-scripts build",

src/templates/Vue InstantSearch 1/package.json

@@ -2,7 +2,6 @@
   "name": "{{name}}",
   "version": "1.0.0",
   "private": true,
-  "main": "src/App.vue",
   "scripts": {
     "start": "vue-cli-service serve --port 3000",
     "build": "vue-cli-service build",

src/templates/Vue InstantSearch/package.json

@@ -2,7 +2,6 @@
   "name": "{{name}}",
   "version": "1.0.0",
   "private": true,
-  "main": "src/App.vue",
   "scripts": {
     "start": "vue-cli-service serve --port 3000",
     "build": "vue-cli-service build",