fix(module:table): remove empty space in custom columns

[vmural]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

https://stackblitz.com/edit/angular-z9xssu

Issue Number: N/A

What is the new behavior?

When using custom fixed-width columns, empty space appears between columns if the total width of the columns is less than the width of the table

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #8022 (ee32301) into master (078aaf9) will increase coverage by 0.01%.
The diff coverage is 0.00%.

❗ Current head ee32301 differs from pull request most recent head 76eb95f. Consider uploading reports for the commit 76eb95f to get more accurate results

@@            Coverage Diff             @@
##           master    #8022      +/-   ##
==========================================
+ Coverage   91.65%   91.66%   +0.01%     
==========================================
  Files         515      515              
  Lines       17641    17641              
  Branches     2790     2790              
==========================================
+ Hits        16168    16170       +2     
+ Misses       1175     1174       -1     
+ Partials      298      297       -1     

Impacted Files	Coverage Δ
...mponents/table/src/cell/custom-column.directive.ts	89.47% <0.00%> (ø)

... and 1 file with indirect coverage changes