build: drop deprecated build tags

src/crypto/rand/rand_arc4random.go

@@ -1,5 +1,4 @@
 //go:build darwin || tinygo.wasm
-// +build darwin tinygo.wasm
 
 // This implementation of crypto/rand uses the arc4random_buf function
 // (available on both MacOS and WASI) to generate random numbers.

src/crypto/rand/rand_baremetal.go

@@ -1,5 +1,4 @@
 //go:build nrf || stm32 || (sam && atsamd51) || (sam && atsame5x)
-// +build nrf stm32 sam,atsamd51 sam,atsame5x
 
 package rand
 

src/crypto/rand/rand_urandom.go

@@ -1,5 +1,4 @@
 //go:build linux && !baremetal && !wasi
-// +build linux,!baremetal,!wasi
 
 // This implementation of crypto/rand uses the /dev/urandom pseudo-file to
 // generate random numbers.