fix(comp:form): repair the form-item-input-content centering（#1019）

[winchesHe]

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What is the current behavior?

The default form controls are all 32 px, and the switch is 28, so swtich is not vertically centered, and so are checkbox, radio, rate, and slider

What is the new behavior?

Other information

the slider lose it width

add flex: 1; to solve

[idux-bot]

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[codecov]

Codecov Report

Merging #1032 (f72d6a1) into main (5d023a8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1032   +/-   ##
=======================================
  Coverage   93.78%   93.78%           
=======================================
  Files         310      310           
  Lines       29648    29648           
  Branches     3510     3510           
=======================================
  Hits        27805    27805           
  Misses       1843     1843           

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[danranVm]

LGTM