nacos.client.MetricsHttpAgent record one request twice

[shalk]

Describe the bug
A clear and concise description of what the bug is.

timer.close() is equivalent with timer.observeDuration(), so timer will observe twice. then we get wrong metric for request count.

we should removetimer.close().

    @Override
    public HttpRestResult<String> httpGet(String path, Map<String, String> headers, Map<String, String> paramValues,
            String encode, long readTimeoutMs) throws Exception {
        Histogram.Timer timer = MetricsMonitor.getConfigRequestMonitor("GET", path, "NA");
        HttpRestResult<String> result;
        try {
            result = httpAgent.httpGet(path, headers, paramValues, encode, readTimeoutMs);
        } catch (IOException e) {
            throw e;
        } finally {
            timer.observeDuration();
            timer.close();
        }
        
        return result;
    }

ref https://github.com/prometheus/client_java#histogram

Expected behavior
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Acutally behavior
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How to Reproduce
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Desktop (please complete the following information):

• OS: [e.g. Centos]
• Version [e.g. nacos-server 1.3.1, nacos-client 1.3.1]
• Module [e.g. naming/config]
• SDK [e.g. original, spring-cloud-alibaba-nacos, dubbo]

Additional context
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