tests: Just check that the version starts with a digit

Our versions look like

4.0.0
4.0b1
4.0.1-535-abfef-dirty

But packagers may want to add more information here, and we don't
really care. Note that we no longer ever set the version to "unknown"
since 5abd0e46f5.

Supersedes #11173

tests/checks/version.fish

@@ -1,2 +1,2 @@
 #RUN: %fish -v
-# CHECK: fish, version {{[-.gabcdeflphat0-9]*(irty)?}}
+# CHECK: fish, version {{[0-9].*}}