removes unused function from numeric-input.jsx named getClasses (#284)

## Summary:
Found an unused function in numeric-input.jsx called getClasses. This specific function was not used in Perseus or webapp. Removed it to practice doing a PR.

Issue: none

## Test plan:
Load the numeric input. Verify it looks correct.

Author: Myranae

Reviewers: jeresig, handeyeco, jeanettehead

Required Reviewers:

Approved By: jeresig

Checks: ✅ codecov/project, ✅ Lint, Flow, and Test (ubuntu-latest, 16.x), ✅ Extract i18n strings (ubuntu-latest, 16.x), ✅ Cypress Coverage (ubuntu-latest, 16.x), ✅ Jest Coverage (ubuntu-latest, 16.x), ✅ Check for .changeset file (ubuntu-latest, 16.x), ✅ gerald, ✅ Check builds for changes in size (ubuntu-latest, 16.x)

Pull Request URL: #284

.changeset/moody-mirrors-clean.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus": patch
+---
+
+removes unused function from numeric-input.jsx named getClasses

packages/perseus/src/widgets/numeric-input.jsx

@@ -10,7 +10,7 @@ import _ from "underscore";
 import InputWithExamples from "../components/input-with-examples.jsx";
 import PossibleAnswers from "../components/possible-answers.jsx";
 import SimpleKeypadInput from "../components/simple-keypad-input.jsx";
-import {ApiOptions, ClassNames as ApiClassNames} from "../perseus-api.jsx";
+import {ApiOptions} from "../perseus-api.jsx";
 import TexWrangler from "../tex-wrangler.js";
 import KhanAnswerTypes from "../util/answer-types.js";
 import KhanMath from "../util/math.js";
@@ -292,18 +292,6 @@ export class NumericInput extends React.Component<Props, State> {
         return [answerBlurb, !!correct];
     };
 
-    getClasses: (boolean, $FlowFixMe) => $FlowFixMe = (correct, rubric) => {
-        const classes = {};
-        classes["perseus-input-size-" + this.props.size] = true;
-        classes["perseus-input-right-align"] = this.props.rightAlign;
-        classes[ApiClassNames.CORRECT] =
-            rubric && correct && this.props.currentValue;
-        classes[ApiClassNames.INCORRECT] =
-            rubric && !correct && this.props.currentValue;
-        classes[ApiClassNames.UNANSWERED] = rubric && !this.props.currentValue;
-        return classes;
-    };
-
     // TODO(Nicole, Jeremy): This is maybe never used and should be removed
     examples: () => $ReadOnlyArray<string> = () => {
         // if the set of specified forms are empty, allow all forms