Add ToUnicode support for similarequal

For \simeq, TeX generates /similarequal instead of Adobe's /asymptoticallyequal; so similarequal needs to be supported too.

In TeX Live 2023, texmf-dist/fonts/map/glyphlist/glyphlist.txt (Adobe Glyph List) contains asymptoticallyequal;2243, but texmf-dist/fonts/map/glyphlist/texglyphlist.txt (Extensions to the Adobe Glyph List for TeX fonts and encodings) contains similarequal;2243. As a consequence, texmf-dist/tex/generic/pdftex/glyphtounicode.tex contains both

\pdfglyphtounicode{asymptoticallyequal}{2243}
\pdfglyphtounicode{similarequal}{2243}

NameToUnicodeTable.h already has

{ 0x2243, "asymptoticallyequal" }

so one just needs to add the missing

{ 0x2243, "similarequal" }