variable-length-quantity: fix grammar (#2043)

Author: ErikSchierboom

exercises/variable-length-quantity/description.md

@@ -5,7 +5,7 @@ Implement variable length quantity encoding and decoding.
 The goal of this exercise is to implement [VLQ](https://en.wikipedia.org/wiki/Variable-length_quantity) encoding/decoding.
 
 In short, the goal of this encoding is to encode integer values in a way that would save bytes.
-Only the first 7 bits of each byte is significant (right-justified; sort of like an ASCII byte).
+Only the first 7 bits of each byte are significant (right-justified; sort of like an ASCII byte).
 So, if you have a 32-bit value, you have to unpack it into a series of 7-bit bytes.
 Of course, you will have a variable number of bytes depending upon your integer.
 To indicate which is the last byte of the series, you leave bit #7 clear.