Remove toLower call on decoded chunk

[zricethezav]

Description

This PR removes a wasteful call to toLower on decoded data. The ahocorasick prefilter matches with case insensitivity: https://github.com/trufflesecurity/trufflehog/blob/rm-tolower-prefilter/pkg/engine/engine.go#L145.

"Testing"

648 results found in both

~/code/trufflesecurity/trufflehog (main) gtime ./trufflehog  git --no-update --no-verification  file://$PWD | grep Found | wc -l
^[[A🐷🔑🐷  TruffleHog. Unearth your secrets. 🐷🔑🐷

real 4.33s
user 17.80s
sys  1.83s
memory:96936KB
cpu 453%
     648
~/code/trufflesecurity/trufflehog (main) gtime ./trufflehog  git --no-update --no-verification  file://$PWD | grep Found | wc -l
~/code/trufflesecurity/trufflehog (main) git checkout rm-tolower-prefilter
Switched to branch 'rm-tolower-prefilter'
~/code/trufflesecurity/trufflehog (rm-tolower-prefilter) go build
~/code/trufflesecurity/trufflehog (rm-tolower-prefilter) gtime ./trufflehog  git --no-update --no-verification  file://$PWD | grep Found | wc -l
🐷🔑🐷  TruffleHog. Unearth your secrets. 🐷🔑🐷

real 4.30s
user 17.06s
sys  1.78s
memory:92876KB
cpu 437%
     648