Fix query string api not respecting source middleware

[silesky]

Fixes bug where addSourceMiddleware would not be applied to events picked up via query string:

example

  analytics.addSourceMiddleware(({ payload, next, integrations }) => {
    console.log(page.type)
    next(payload);
  };);
  analytics.load()
  analytics.page()

[changeset-bot]

🦋 Changeset detected

Latest commit: d735bac

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@segment/analytics-next	Patch

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.

Project coverage is 34.15%. Comparing base (00a736f) to head (d735bac).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
packages/browser/src/browser/index.ts	0.00%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1207      +/-   ##
==========================================
- Coverage   34.20%   34.15%   -0.06%     
==========================================
  Files         157      157              
  Lines        4259     4266       +7     
  Branches      973      973              
==========================================
  Hits         1457     1457              
- Misses       2802     2809       +7     

Flag	Coverage Δ
browser	10.46% <0.00%> (-0.03%)	⬇️
core	89.86% <ø> (ø)
node	82.02% <ø> (ø)

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