URL field on HTTPRequestLog should have max length of 2048

[nicpottier]

Blowing up when calling Classifiers like Wit which use GET attributes on their URL

[codecov]

Codecov Report

Merging #3337 (e640189) into main (0a94ef6) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main     #3337   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          367       368    +1     
  Lines        24592     24596    +4     
=========================================
+ Hits         24592     24596    +4     

Impacted Files	Coverage Δ
...a/request_logs/migrations/0009_resize_url_field.py	100.00% <100.00%> (ø)
temba/request_logs/models.py	100.00% <100.00%> (ø)

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