chore(deps): replace custom bcp47_strict_language_tag with upstream

go-playground/validator@b599053 added bcp47_strict_language_tag as a
built-in validator (go-playground/validator#1489), so our copy is now
redundant. Drop validators/bcp47.go and its tests; update bcp47_keys to
delegate to the built-in tag via a package-level Validate instance.

Closes italia#341, closes italia#342.

Author: creed-bratton

go.mod

@@ -5,11 +5,10 @@ require (
 	github.com/github/go-spdx/v2 v2.4.0
 	github.com/go-playground/locales v0.14.1
 	github.com/go-playground/universal-translator v0.18.1
-	github.com/go-playground/validator/v10 v10.30.2
+	github.com/go-playground/validator/v10 v10.30.3-0.20260409172054-b599053e6029
 	github.com/goccy/go-yaml v1.19.2
 	github.com/italia/httpclient-lib-go v0.0.3-0.20260316100201-5dd490bc4896
 	github.com/rivo/uniseg v0.4.7
-	golang.org/x/text v0.35.0
 )
 
 require (
@@ -19,6 +18,7 @@ require (
 	github.com/tomnomnom/linkheader v0.0.0-20180905144013-02ca5825eb80 // indirect
 	golang.org/x/crypto v0.49.0 // indirect
 	golang.org/x/sys v0.42.0 // indirect
+	golang.org/x/text v0.35.0 // indirect
 )
 
 go 1.25.0

go.sum

@@ -13,8 +13,8 @@ github.com/go-playground/locales v0.14.1 h1:EWaQ/wswjilfKLTECiXz7Rh+3BjFhfDFKv/o
 github.com/go-playground/locales v0.14.1/go.mod h1:hxrqLVvrK65+Rwrd5Fc6F2O76J/NuW9t0sjnWqG1slY=
 github.com/go-playground/universal-translator v0.18.1 h1:Bcnm0ZwsGyWbCzImXv+pAJnYK9S473LQFuzCbDbfSFY=
 github.com/go-playground/universal-translator v0.18.1/go.mod h1:xekY+UJKNuX9WP91TpwSH2VMlDf28Uj24BCp08ZFTUY=
-github.com/go-playground/validator/v10 v10.30.2 h1:JiFIMtSSHb2/XBUbWM4i/MpeQm9ZK2xqPNk8vgvu5JQ=
-github.com/go-playground/validator/v10 v10.30.2/go.mod h1:mAf2pIOVXjTEBrwUMGKkCWKKPs9NheYGabeB04txQSc=
+github.com/go-playground/validator/v10 v10.30.3-0.20260409172054-b599053e6029 h1:yPDgnVvfx/0o9KyD4lghxxBMXZVo8UKogLSxl/Tz3UU=
+github.com/go-playground/validator/v10 v10.30.3-0.20260409172054-b599053e6029/go.mod h1:mAf2pIOVXjTEBrwUMGKkCWKKPs9NheYGabeB04txQSc=
 github.com/goccy/go-yaml v1.19.2 h1:PmFC1S6h8ljIz6gMRBopkjP1TVT7xuwrButHID66PoM=
 github.com/goccy/go-yaml v1.19.2/go.mod h1:XBurs7gK8ATbW4ZPGKgcbrY1Br56PdM69F7LkFRi1kA=
 github.com/italia/httpclient-lib-go v0.0.3-0.20260316100201-5dd490bc4896 h1:7JV5L0I++QbIMdVjU467tUW+dQnX6hdmhMLZAjrehjQ=