fix: replace .english.md extension with .md

curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-317-firecracker.md

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+---
+id: 5900f4aa1000cf542c50ffbc
+challengeType: 5
+title: 'Problem 317: Firecracker'
+forumTopicId: 301973
+---
+
+## Description
+<section id='description'>
+A firecracker explodes at a height of 100 m above level ground. It breaks into a large number of very small fragments, which move in every direction; all of them have the same initial velocity of 20 m/s.
+
+
+We assume that the fragments move without air resistance, in a uniform gravitational field with g=9.81 m/s2.
+
+
+Find the volume (in m3) of the region through which the fragments move before reaching the ground.
+Give your answer rounded to four decimal places.
+</section>
+
+## Instructions
+<section id='instructions'>
+
+</section>
+
+## Tests
+<section id='tests'>
+
+```yml
+tests:
+  - text: <code>euler317()</code> should return 1856532.8455.
+    testString: assert.strictEqual(euler317(), 1856532.8455);
+
+```
+
+</section>
+
+## Challenge Seed
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+function euler317() {
+
+  return true;
+}
+
+euler317();
+```
+
+</div>
+
+
+
+</section>
+
+## Solution
+<section id='solution'>
+
+```js
+// solution required
+```
+
+</section>