Use texmath 0.12.3.

pandoc.cabal

@@ -486,7 +486,7 @@ library
                  syb                   >= 0.1      && < 0.8,
                  tagsoup               >= 0.14.6   && < 0.15,
                  temporary             >= 1.1      && < 1.4,
-                 texmath               >= 0.12.2   && < 0.12.3,
+                 texmath               >= 0.12.3   && < 0.12.4,
                  text                  >= 1.1.1.0  && < 1.3,
                  text-conversions      >= 0.3      && < 0.4,
                  time                  >= 1.5      && < 1.10,

stack.yaml

@@ -16,9 +16,7 @@ extra-deps:
 - random-1.2.0
 - xml-conduit-1.9.1.1
 - unicode-collation-0.1.3
-# - texmath-0.12.2
-- git: https://github.com/jgm/texmath
-  commit: 0c34bb7d229389adc62bcbfe20cfbfdc0c8ccc8d
+- texmath-0.12.3
 # - citeproc-0.3.0.9
 - git: https://github.com/jgm/citeproc
   commit: f33b370bd1ab5ad5140720369c0586041e433a47