Don't escape forward-slashes.
It appears that this code incorrectly re-implemented logic from
serde_json, which does have the code to escape a forward-slash, but
never uses it: https://github.com/serde-rs/json/pull/898.
diff --git a/third_party/src/ser.rs b/third_party/src/ser.rs
index 6e271fc..3fa22b2 100644
--- a/third_party/src/ser.rs
+++ b/third_party/src/ser.rs
@@ -364,7 +364,6 @@
'\n' => vec!['\\', 'n'],
'\r' => vec!['\\', 'r'],
'\t' => vec!['\\', 't'],
- '/' => vec!['\\', '/'],
'\\' => vec!['\\', '\\'],
'\u{0008}' => vec!['\\', 'b'],
'\u{000c}' => vec!['\\', 'f'],
