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

curriculum/challenges/en/08-coding-interview-prep/project-euler/problem-209-circular-logic.en.md

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+---
+id: 5900f43e1000cf542c50ff4f
+challengeType: 5
+title: 'Problem 209: Circular Logic'
+---
+
+## Description
+<section id='description'>
+A k-input binary truth table is a map from k input bits
+(binary digits, 0 [false] or 1 [true]) to 1 output bit. For example, the 2-input binary truth tables for the logical AND and XOR functions are:
+
+x
+y
+x AND y000010100111x
+y
+x XOR y000011101110How many 6-input binary truth tables, τ, satisfy the formula
+
+τ(a, b, c, d, e, f) AND τ(b, c, d, e, f, a XOR (b AND c)) = 0
+for all 6-bit inputs (a, b, c, d, e, f)?
+</section>
+
+## Instructions
+<section id='instructions'>
+
+</section>
+
+## Tests
+<section id='tests'>
+
+```yml
+- text: <code>euler209()</code> should return 15964587728784.
+  testString: 'assert.strictEqual(euler209(), 15964587728784, ''<code>euler209()</code> should return 15964587728784.'');'
+
+```
+
+</section>
+
+## Challenge Seed
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+function euler209() {
+  // Good luck!
+  return true;
+}
+
+euler209();
+```
+
+</div>
+
+
+
+</section>
+
+## Solution
+<section id='solution'>
+
+```js
+// solution required
+```
+</section>