🎨 Fix UI problems in participants page

[ambarvm]

Changes proposed in this pull request:

• Fix pagination button wrapping to next line on medium-sized screens
• Fix cards overlapping on small screens

• Link to live demo: http://pr-298-evalai.surge.sh

Before	After

[codecov-io]

Codecov Report

Merging #298 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #298      +/-   ##
==========================================
+ Coverage   50.62%   50.64%   +0.02%     
==========================================
  Files          66       66              
  Lines        3771     3771              
  Branches      444      444              
==========================================
+ Hits         1909     1910       +1     
+ Misses       1767     1766       -1     
  Partials       95       95

Impacted Files	Coverage Δ
...bliclists/challengelist/challengelist.component.ts	47.57% <0%> (+0.97%)	⬆️

Impacted Files	Coverage Δ
...bliclists/challengelist/challengelist.component.ts	47.57% <0%> (+0.97%)	⬆️

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