Deprecation: CFB encryption

As part of https://github.com/grafana/grafana/pull/102759, golangci-lint pointed out that Go 1.24 has deprecated CFB encryption. ``` Error: pkg/services/encryption/provider/cipher_aescfb.go:41:12: SA1019: cipher.NewCFBEncrypter has been deprecated since Go 1.24 and an alternative has been available since Go 1.2: CFB mode is not authenticated, which generally enables active attacks to manipulate and recover the plaintext. It is recommended that applications use [AEAD] modes instead. The standard library implementation of CFB is also unoptimized and not validated as part of the FIPS 140-3 module. If an unauthenticated [Stream] mode is required, use [NewCTR] instead. (staticcheck) stream := cipher.NewCFBEncrypter(block, iv) ^ Error: pkg/services/encryption/provider/decipher_aes.go:62:12: SA1019: cipher.NewCFBDecrypter has been deprecated since Go 1.24 and an alternative has been available since Go 1.2: CFB mode is not authenticated, which generally enables active attacks to manipulate and recover the plaintext. It is recommended that applications use [AEAD] modes instead. The standard library implementation of CFB is also unoptimized and not validated as part of the FIPS 140-3 module. If an unauthenticated [Stream] mode is required, use [NewCTR] instead. (staticcheck) stream := cipher.NewCFBDecrypter(block, iv) ^ Error: pkg/util/encryption.go:105:12: SA1019: cipher.NewCFBDecrypter has been deprecated since Go 1.24 and an alternative has been available since Go 1.2: CFB mode is not authenticated, which generally enables active attacks to manipulate and recover the plaintext. It is recommended that applications use [AEAD] modes instead. The standard library implementation of CFB is also unoptimized and not validated as part of the FIPS 140-3 module. If an unauthenticated [Stream] mode is required, use [NewCTR] instead. (staticcheck) stream := cipher.NewCFBDecrypter(block, iv) ^ Error: pkg/util/encryption.go:1[39](http…