fix JSONReaderUTF8 nameValue1 for issue 2049

[milabi]

fix(JSONReaderUTF8): 修复name的length=14位时，nameValue1计算

What this PR does / why we need it?

#2409

Summary of your change

map反序列化时，14位的key在对nameValue1计算有误，其第8位计算下标应为7，而不是8

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

[CLAassistant]

All committers have signed the CLA.

[wenshao]

可以补充一个testcase么？

[milabi]

@wenshao 可以我稍后提交一下

[milabi]

可以补充一个testcase么？

已经补充了testcase，请问这个会在哪个版本中修复，大概会在什么时候发版？

[wenshao]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson2/fastjson2/2.0.49-SNAPSHOT/
2.0.49版本预计在4月下旬发布，可能是4月21日