Bump to 0.4.0. (#59)

Author: jmjoy

Cargo.lock

@@ -21,7 +21,7 @@ members = [
 
 [package]
 name = "skywalking-php"
-version = "0.4.0-dev"
+version = "0.4.0"
 authors = ["Apache Software Foundation", "jmjoy <jmjoy@apache.org>", "Yanlong He <heyanlong@apache.org>"]
 description = "Apache SkyWalking PHP Agent."
 edition = "2021"

Cargo.toml

@@ -224,7 +224,7 @@ The text of each license is the standard Apache 2.0 license.
     https://crates.io/crates/prost-types/0.11.6 0.11.6 Apache-2.0
     https://crates.io/crates/scripts/0.0.0 0.0.0 Apache-2.0
     https://crates.io/crates/skywalking/0.6.0 0.6.0 Apache-2.0
-    https://crates.io/crates/skywalking-php/0.4.0-dev 0.4.0-dev Apache-2.0
+    https://crates.io/crates/skywalking-php/0.4.0 0.4.0 Apache-2.0
     https://crates.io/crates/sync_wrapper/0.1.1 0.1.1 Apache-2.0
 
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