chore!: Rename directory day1a to day1.

diff --git a/day1a/git_hooks/post-commit b/day1/git_hooks/post-commit
similarity index 100%
rename from day1a/git_hooks/post-commit
rename to day1/git_hooks/post-commit

diff --git a/day1a/in.txt b/day1/in.txt
similarity index 100%
rename from day1a/in.txt
rename to day1/in.txt

diff --git a/day1a/input.txt b/day1/input.txt
similarity index 100%
rename from day1a/input.txt
rename to day1/input.txt

diff --git a/day1a/main.go b/day1/main.go
similarity index 100%
rename from day1a/main.go
rename to day1/main.go