Fix image paths in spec markdown

Change-Id: I979c864cc07cc6d0950d11548c1243da8c289a8c
Reviewed-on: https://pigweed-review.googlesource.com/c/open-dice/+/31970
Reviewed-by: Ali Zhang <alizhang@google.com>
diff --git a/docs/specification.md b/docs/specification.md
index 477b118..5c746f2 100644
--- a/docs/specification.md
+++ b/docs/specification.md
@@ -89,7 +89,7 @@
 place of the UDS to compute the subsequent CDI values. See
 [Layering Details](#layering-details).
 
-![Architecture Diagram](images/architecture.png)
+![Architecture Diagram](../images/architecture.png)
 
 ## Use Cases
 
@@ -203,7 +203,7 @@
 As an example, if the CDI private key were used to sign a leaf certificate for
 an attestation key, the certificate chain may look like this:
 
-![Single Layer Certificate Chain Diagram](images/single-layer-cert-chain.png)
+![Single Layer Certificate Chain Diagram](../images/single-layer-cert-chain.png)
 
 ## High-level DICE Flow
 
@@ -422,7 +422,7 @@
 When generating certificates, the authority is the previous CDI key pair and the
 certificates chain together. So the certificate chain may look like this:
 
-![Multi Layer Certificate Chain Diagram](images/multi-layer-cert-chain.png)
+![Multi Layer Certificate Chain Diagram](../images/multi-layer-cert-chain.png)
 
 ## UDS Details