Go 1.17 and earlier used a different syntax for build constraint comments,
starting with "+build". Go 1.18 changed this to the modern "go:build" form
as part of standardizing the structure of toolchain directive comments,
and so for a while it was convention to include comments in both styles
to allow building with both old and new Go compilers.
However, Go 1.17 is no longer supported, and regardless of that we only
expect OpenTofu to be built with the specific version we have selected
in "go.mod" and ".go-version" anyway, so we no longer need the legacy form
of these comments: the all supported Go toolchains now support the new
form, which this commit retains.
golangci-lint v2.6.0 includes a check for this legacy form, so removing
this will also allow us to upgrade to a newer version of that linter
aggregator in a future commit.
Signed-off-by: Martin Atkins <mart@degeneration.co.uk>
