build: 修改 umd 构建配置以避免 json-schema 重复打包

[Grapedge]

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What have you changed?

将 rollup 配置中将 @formily/json-schema 设置为 external。
Fixed #3465

[codecov]

Codecov Report

Base: 96.17% // Head: 96.17% // No change to project coverage 👍

Coverage data is based on head (7f593bf) compared to base (3a3db05).
Patch has no changes to coverable lines.

Additional details and impacted files

@@              Coverage Diff              @@
##           formily_next    #3467   +/-   ##
=============================================
  Coverage         96.17%   96.17%           
=============================================
  Files               152      152           
  Lines              6596     6596           
  Branches           1834     1777   -57     
=============================================
  Hits               6344     6344           
  Misses              252      252           

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