guix: bump recommended hash for manual installation

Tracks time-machine bump in 298389e.

Author: Sjors

contrib/guix/INSTALL.md

@@ -384,8 +384,9 @@ cd guix
 ```
 
 You will likely want to build the latest release, however, if the latest release
-when you're reading this is still 1.2.0 then you may want to use 95aca29 instead
-to avoid a problem in the GnuTLS test suite.
+when you're reading this is still 1.3.0 then you may want to use 998eda30 instead
+to avoid the issues described in [#25099](
+https://github.com/bitcoin/bitcoin/pull/25099).
 
 ```
 git branch -a -l 'origin/version-*'  # check for the latest release