Merge pull request #1768 from mozilla/dependabot/cargo/flate2-1.0.21

Bump flate2 from 1.0.19 to 1.0.21

Cargo.lock

@@ -190,9 +190,9 @@ dependencies = [
 
 [[package]]
 name = "flate2"
-version = "1.0.19"
+version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7411863d55df97a419aa64cb4d2f167103ea9d767e2c54a1868b7ac3f6b47129"
+checksum = "80edafed416a46fb378521624fab1cfa2eb514784fd8921adbe8a8d8321da811"
 dependencies = [
  "cfg-if 1.0.0",
  "crc32fast",