fix(challenge-md): Fix file names and preserve challenge order in meta.json

curriculum/challenges/en/08-coding-interview-prep/project-euler/problem-135-same-differences.en.md

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+---
+id: 5900f3f31000cf542c50ff06
+challengeType: 5
+title: 'Problem 135: Same differences'
+---
+
+## Description
+<section id='description'>
+Given the positive integers, x, y, and z, are consecutive terms of an arithmetic progression, the least value of the positive integer, n, for which the equation, x2 − y2 − z2 = n, has exactly two solutions is n = 27:
+342 − 272 − 202 = 122 − 92 − 62 = 27
+It turns out that n = 1155 is the least value which has exactly ten solutions.
+How many values of n less than one million have exactly ten distinct solutions?
+</section>
+
+## Instructions
+<section id='instructions'>
+
+</section>
+
+## Tests
+<section id='tests'>
+
+```yml
+- text: <code>euler135()</code> should return 4989.
+  testString: 'assert.strictEqual(euler135(), 4989, ''<code>euler135()</code> should return 4989.'');'
+
+```
+
+</section>
+
+## Challenge Seed
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+function euler135() {
+  // Good luck!
+  return true;
+}
+
+euler135();
+```
+
+</div>
+
+
+
+</section>
+
+## Solution
+<section id='solution'>
+
+```js
+// solution required
+```
+</section>