Set charset instead of encoding in testlog content type

`encoding` doesn't do anything, the correct property is `charset`.

Author: fmeum

agent/src/artifact/upload.rs

@@ -639,7 +639,7 @@ fn upload_test_log(
         cwd.as_ref().map(|pb| pb.as_path()),
         &artifact,
         mode,
-        Some("text/plain;encoding=utf-8"),
+        Some("text/plain;charset=utf-8"),
     );
 }
 

agent/tests/artifact/upload.rs

@@ -19,7 +19,7 @@ fn test_logs_uploaded_to_buildkite() -> Result<()> {
     ]);
     cmd.assert()
         .success()
-        .stdout(predicates::ord::eq("buildkite-agent artifact upload --content-type text/plain;encoding=utf-8 src\\test\\shell\\bazel\\resource_compiler_toolchain_test\\test.log\n"));
+        .stdout(predicates::ord::eq("buildkite-agent artifact upload --content-type text/plain;charset=utf-8 src\\test\\shell\\bazel\\resource_compiler_toolchain_test\\test.log\n"));
 
     Ok(())
 }
@@ -37,7 +37,7 @@ fn test_logs_uploaded_to_buildkite() -> Result<()> {
     ]);
     cmd.assert()
         .success()
-        .stdout(predicates::ord::eq("buildkite-agent artifact upload --content-type text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log\n"));
+        .stdout(predicates::ord::eq("buildkite-agent artifact upload --content-type text/plain;charset=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log\n"));
 
     Ok(())
 }
@@ -139,7 +139,7 @@ fn test_logs_deduplicated() -> Result<()> {
     ]);
     cmd.assert()
         .success()
-        .stdout(predicates::str::contains("buildkite-agent artifact upload --content-type text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log").count(1));
+        .stdout(predicates::str::contains("buildkite-agent artifact upload --content-type text/plain;charset=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log").count(1));
 
     Ok(())
 }
@@ -178,7 +178,7 @@ fn test_running_json_file() -> Result<()> {
 
         cmd.assert()
         .success()
-        .stdout(predicates::str::contains("buildkite-agent artifact upload --content-type text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log"));
+        .stdout(predicates::str::contains("buildkite-agent artifact upload --content-type text/plain;charset=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log"));
         Ok(())
     })
 }