doc: add note about x509sha1 removal in 1.24

Updates #62048

Change-Id: I17f462841a80db2216806147f0a0548f95c5e21a
Reviewed-on: https://go-review.googlesource.com/c/go/+/586718
Auto-Submit: Roland Shoemaker <[email protected]>
Reviewed-by: Filippo Valsorda <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: rolandshoemaker

doc/next/6-stdlib/99-minor/crypto/x509/62048.md

@@ -0,0 +1,4 @@
+The [`x509sha1` GODEBUG setting](/pkg/crypto/x509#InsecureAlgorithmError) will
+be removed in the next Go major release (Go 1.24). This will mean that crypto/x509
+will no longer support verifying signatures on certificates that use SHA-1 based
+signature algorithms.