Auto merge of #18446 - bzbarsky:update-cssparser, r=SimonSapin

Update rust-cssparser to 0.20.2.

This reduces memory consumption of list-valued properties in the common case of one entry in the list.

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ports/geckolib/Cargo.toml

@@ -15,7 +15,7 @@ gecko_debug = ["style/gecko_debug"]
 
 [dependencies]
 atomic_refcell = "0.1"
-cssparser = "0.20"
+cssparser = "0.20.2"
 env_logger = {version = "0.4", default-features = false} # disable `regex` to reduce code size
 libc = "0.2"
 log = {version = "0.3.5", features = ["release_max_level_info"]}