Remove unnecessary error types

[kalaiyarasiganeshalingam]

Purpose

$Subject related to the issue 991

[codecov]

Codecov Report

Merging #103 (218777a) into master (09822b7) will not change coverage.
The diff coverage is 50.00%.

@@            Coverage Diff            @@
##             master     #103   +/-   ##
=========================================
  Coverage     90.95%   90.95%           
  Complexity       31       31           
=========================================
  Files             5        5           
  Lines           221      221           
  Branches         87       87           
=========================================
  Hits            201      201           
  Misses           20       20           

Impacted Files	Coverage Δ	Complexity Δ
cache-ballerina/cache_errors.bal	83.33% <50.00%> (ø)	1.00 <0.00> (ø)

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