RUM-1052: Delete old shrinked mapping file before writing to it

[0xnm]

What does this PR do?

There is a bug that old shrinked mapping file wasn't deleted before doing the shrinking again. This PR fixes it.

Review checklist (to be filled by reviewers)

• [ ] Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• [ ] Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• [ ] Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

Merging #189 (e1b760a) into develop (8025b34) will increase coverage by 0.07%. The diff coverage is 100.00%.

@@              Coverage Diff              @@
##             develop     #189      +/-   ##
=============================================
+ Coverage      86.81%   86.87%   +0.07%     
- Complexity       177      178       +1     
=============================================
  Files             21       21              
  Lines            576      579       +3     
  Branches          75       76       +1     
=============================================
+ Hits             500      503       +3     
  Misses            49       49              
  Partials          27       27              

Files Changed	Coverage Δ
...m/datadog/gradle/plugin/DdMappingFileUploadTask.kt	88.65% <100.00%> (+0.16%)	:arrow_up:

... and 1 file with indirect coverage changes