[canvas] unify eslint config in .eslintrc.js (#25260)

Simply remove the remaining eslint config files from canvas and merge with other canvas related overrides in `.eslintrc.js`

.eslintrc.js

@@ -447,5 +447,17 @@ module.exports = {
         ],
       },
     },
+    {
+      files: ['x-pack/plugins/canvas/public/**/*'],
+      env: {
+        browser: true,
+      },
+    },
+    {
+      files: ['x-pack/plugins/canvas/canvas_plugin_src/lib/flot-charts/**/*'],
+      env: {
+        jquery: true,
+      },
+    },
   ],
 };

x-pack/plugins/canvas/canvas_plugin_src/lib/flot-charts/.eslintrc

@@ -1,2 +0,0 @@
-env:
-  jquery: true

x-pack/plugins/canvas/public/.eslintrc

@@ -1,2 +0,0 @@
-env:
-  browser: true