Modernize docs/assets/js/search.js (#10621)

- reformated file with eslint's --fix
- did some minor rule adjustments
- removed unneccesary console debug
- fixed a typo

.eslintrc

@@ -36,6 +36,8 @@ rules:
   max-len: [0]
   newline-per-chained-call: [0]
   no-alert: [0]
+  no-cond-assign: [2, except-parens]
+  no-console: [1, {allow: [info, warn, error]}]
   no-continue: [0]
   no-mixed-operators: [0]
   no-multi-assign: [0]