remove unnecessary \up (upright) from some latex abbrevs (e.g. \upM…

…u -> \Mu) (#50925)

Closes #50911.  Closes #50913.

There were a few oddball symbols prefixed with `\up` (for "upright") for
no reason that I can tell, ala the LaTeX "upgreek" package, even though
we don't use an `\up` prefix for other upright Greek letters (e.g. we
have `\alpha`, not `\upalpha`, even though it isn't italicized — we have
`\italpha` for italic alpha).

Not breaking since this is just a UI thing.

(In practice, I doubt many people use these symbols. e.g. `\upMu` is
`Μ`, which looks a lot like the Latin `M`. But there is no reason to
have the `\up` prefix here. It seems to have just been an automated
abbreviation-import snafu. And [`\upkoppa 'ϟ'`
(U+O3DF)](https://www.compart.com/en/unicode/U+03DF) is visually quite
distinctive though I've never seen it used in math, not to mention
lowercase — it's definitely goofy to have an `\up` prefix for it.)

stdlib/REPL/src/latex_symbols.jl

@@ -984,17 +984,16 @@ const latex_symbols = Dict(
     "\\droang" => "̚",  # left angle above (non-spacing)
     "\\wideutilde" => "̰",  # under tilde accent (multiple characters and non-spacing)
     "\\not" => "̸",  # combining long solidus overlay
-    "\\upMu" => "Μ",  # capital mu, greek
-    "\\upNu" => "Ν",  # capital nu, greek
-    "\\upOmicron" => "Ο",  # capital omicron, greek
-    "\\upepsilon" => "ε",  # rounded small epsilon, greek
-    "\\upomicron" => "ο",  # small omicron, greek
-    "\\upvarbeta" => "ϐ",  # rounded small beta, greek
-    "\\upoldKoppa" => "Ϙ",  # greek letter archaic koppa
-    "\\upoldkoppa" => "ϙ",  # greek small letter archaic koppa
-    "\\upstigma" => "ϛ",  # greek small letter stigma
-    "\\upkoppa" => "ϟ",  # greek small letter koppa
-    "\\upsampi" => "ϡ",  # greek small letter sampi
+    "\\Mu" => "Μ",  # capital mu, greek
+    "\\Nu" => "Ν",  # capital nu, greek
+    "\\Omicron" => "Ο",  # capital omicron, greek
+    "\\omicron" => "ο",  # small omicron, greek
+    "\\varbeta" => "ϐ",  # rounded small beta, greek
+    "\\oldKoppa" => "Ϙ",  # greek letter archaic koppa
+    "\\oldkoppa" => "ϙ",  # greek small letter archaic koppa
+    "\\stigma" => "ϛ",  # greek small letter stigma
+    "\\koppa" => "ϟ",  # greek small letter koppa
+    "\\sampi" => "ϡ",  # greek small letter sampi
     "\\tieconcat" => "⁀",  # character tie, z notation sequence concatenation
     "\\leftharpoonaccent" => "⃐",  # combining left harpoon above
     "\\rightharpoonaccent" => "⃑",  # combining right harpoon above