test: refresh Shannon snapshot after merging main

CI checks out a merge of the PR head with main, and main advanced 8
commits since this branch was cut — including #201 (contextual digit
runs), #240 and #253 (markdown fixes). Those change extraction output,
so a snapshot generated on the unmerged branch could not match; the
Test job failed on the merge commit while passing on the branch itself.

The merged behaviour is better: the footnote marker '2' before
'Hartley, R. V. L.' is now recovered instead of dropped.

950 tests pass on the merged tree, clippy clean.

Author: abimaelmartell

tests/snapshots/shannon-entropy-p1-2.md

@@ -22,7 +22,7 @@ J. W. Tukey. A device with two stable positions, such as a relay or a flip-flop
 
 log₂*M* = log₁₀*M*= log₁₀2 = 3:32 log₁₀*M*;
 
-1 Nyquist, H., “Certain Factors Affecting Telegraph Speed,” *Bell System Technical Journal,* April 1924, p. 324; “Certain Topics in Telegraph Transmission Theory,” *A.I.E.E. Trans.,* v. 47, April 1928, p. 617. Hartley, R. V. L., “Transmission of Information,” *Bell System Technical Journal,* July 1928, p. 535.
+1 Nyquist, H., “Certain Factors Affecting Telegraph Speed,” *Bell System Technical Journal,* April 1924, p. 324; “Certain Topics in Telegraph Transmission Theory,” *A.I.E.E. Trans.,* v. 47, April 1928, p. 617. 2 Hartley, R. V. L., “Transmission of Information,” *Bell System Technical Journal,* July 1928, p. 535.
 
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