Normalize focused goal output

Merge the "1 focused goal" line with the subsequent "(shelved: 1)" line,
since this is the new output in Coq 8.15+.

Iris does not currently produce this output, since no test calls `Show`
with shelved goals, but this future-proofs the test normalization.

test-normalizer.sed

@@ -2,3 +2,5 @@
 s/(simple_intropattern)/(intropattern)/g
 # adjust for https://github.com/coq/coq/pull/13656
 s/subgoal/goal/g
+# merge with subsequent line for https://github.com/coq/coq/pull/14999
+/[0-9]* focused goals\?$/{N;s/\n */ /;}