*: Remove use of deprecated io/util

_examples/commit/main.go

_examples/common_test.go

_examples/sha256/main.go

_examples/tag-create-push/main.go

config/config.go

example_test.go

plumbing/format/gitattributes/attributes.go

plumbing/format/gitignore/dir.go

plumbing/format/idxfile/decoder_test.go

plumbing/format/idxfile/encoder_test.go

plumbing/format/idxfile/writer_test.go

plumbing/format/index/decoder.go

plumbing/format/objfile/reader_test.go

plumbing/format/packfile/delta_test.go

plumbing/format/packfile/encoder_test.go

plumbing/format/packfile/parser.go

plumbing/format/packfile/scanner.go

plumbing/memory_test.go

plumbing/object/blob_test.go

plumbing/object/commit_test.go