fix: replace .english.md extension with .md

curriculum/challenges/english/10-coding-interview-prep/rosetta-code/greatest-common-divisor.md

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+---
+title: Greatest common divisor
+id: 5a23c84252665b21eecc7e82
+challengeType: 5
+forumTopicId: 302277
+---
+
+## Description
+<section id='description'>
+Write a function that returns the greatest common divisor of two integers.
+</section>
+
+## Instructions
+<section id='instructions'>
+
+</section>
+
+## Tests
+<section id='tests'>
+
+```yml
+tests:
+  - text: <code>gcd</code> should be a function.
+    testString: assert(typeof gcd=='function');
+  - text: <code>gcd(24,36)</code> should return a number.
+    testString: assert(typeof gcd(24,36)=='number');
+  - text: <code>gcd(24,36)</code> should return <code>12</code>.
+    testString: assert.equal(gcd(24,36),12);
+  - text: <code>gcd(30,48)</code> should return <code>6</code>.
+    testString: assert.equal(gcd(30,48),6);
+  - text: <code>gcd(10,15)</code> should return <code>5</code>.
+    testString: assert.equal(gcd(10,15),5);
+  - text: <code>gcd(100,25)</code> should return <code>25</code>.
+    testString: assert.equal(gcd(100,25),25);
+  - text: <code>gcd(13,250)</code> should return <code>1</code>.
+    testString: assert.equal(gcd(13,250),1);
+  - text: <code>gcd(1300,250)</code> should return <code>50</code>.
+    testString: assert.equal(gcd(1300,250),50);
+
+```
+
+</section>
+
+## Challenge Seed
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+function gcd(a, b) {
+
+}
+```
+
+</div>
+
+
+
+</section>
+
+## Solution
+<section id='solution'>
+
+
+```js
+function gcd(a, b) {
+  return b==0 ? Math.abs(a):gcd(b, a % b);
+}
+
+```
+
+</section>