pinnedpubkey.d: fix formatting for version support lists

[jay]

Closes #xxxx

---

before: manpage.html

after: manpage.html

---

alternately:

I'm not sure how to get it more compact without the vertical space and I get inconsistent results with .RS/.RE depending on whether I'm viewing the manpage generated by nroff or the manpage html generated by roffit

PEM/DER support:
.RS
7.39.0: OpenSSL, GnuTLS and GSKit
.RE
.RS
7.43.0: NSS and wolfSSL
.RE
.RS
7.47.0: mbedtls
.RE
.IP
sha256 support:
.RS
7.44.0: OpenSSL, GnuTLS, NSS and wolfSSL
.RE
.RS
7.47.0: mbedtls
.RE
.IP
Other SSL backends not supported.