bionic-amd64-tf-m-build: Update to m2r2 0.3.2

"m2r2" package (as required for TF-M docs generation) has got a dependency
on "mistune" package, which in the meantime seems to have had a non
backwards compatible update. Version 0.3.2 of "m2r2" has the only change
comparing to the previously used 0.3.1 - pinning the right version of
"mistune" as a dependency:

https://github.com/CrossNox/m2r2/compare/v0.3.1...v0.3.2

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I1ddceb21ec881a1722e75488d07191b4856f741e
1 file changed