Drop use of html5shiv

Fixes #3367

app/assets/config/manifest.js

@@ -19,8 +19,6 @@
 
 //= link_directory ../../../vendor/assets/polyfill .js
 
-//= link html5shiv/dist/html5shiv.js
-
 //= link leaflet/dist/images/marker-icon.png
 //= link leaflet/dist/images/marker-icon-2x.png
 //= link leaflet/dist/images/marker-shadow.png

app/views/layouts/_head.html.erb

@@ -1,7 +1,6 @@
 <%= tag.head :data => application_data do %>
   <meta http-equiv="X-UA-Compatible" content="IE=edge" />
   <meta name="viewport" content="width=device-width, minimum-scale=1.0, maximum-scale=1.0" />
-  <%= javascript_include_tag "html5shiv/dist/html5shiv" unless browser.html5? %>
   <%= javascript_include_tag "es5" unless browser.es5? %>
   <%= javascript_include_tag "es6" unless browser.es6? %>
   <%= javascript_include_tag "application" %>

package.json

@@ -3,7 +3,6 @@
   "private": true,
   "dependencies": {
     "bs-custom-file-input": "^1.3.4",
-    "html5shiv": "^3.7.3",
     "jquery-simulate": "^1.0.2",
     "js-cookie": "^3.0.0",
     "leaflet": "^1.6.0",

yarn.lock

@@ -384,11 +384,6 @@ has@^1.0.3:
   dependencies:
     function-bind "^1.1.1"
 
-html5shiv@^3.7.3:
-  version "3.7.3"
-  resolved "https://registry.yarnpkg.com/html5shiv/-/html5shiv-3.7.3.tgz#d78a84a367bcb9a710100d57802c387b084631d2"
-  integrity sha1-14qEo2e8uacQEA1XgCw4ewhGMdI=
-
 ignore@^4.0.6:
   version "4.0.6"
   resolved "https://registry.yarnpkg.com/ignore/-/ignore-4.0.6.tgz#750e3db5862087b4737ebac8207ffd1ef27b25fc"