webp-container-spec.txt: replace &amp; with &
this conversion is handled by markdown processors
@@ -54,8 +54,8 @@ when, and only when, they appear in all capitals, as shown here.
Bit numbering in chunk diagrams starts at `0` for the most significant bit
('MSB 0') as described in [RFC 1166][].
-Terminology &amp; Basics
-------------------------
+Terminology & Basics
+--------------------
A WebP file contains either a still image (i.e., an encoded matrix of pixels)
or an [animation](#animation). Optionally, it can also contain transparency
