Remove omikron from math tests.

The letter Omikron is not available in TeX math mode because
it looks like the latin O and hence not used as mathematical symbol.

autotests/export/latex/unicodesymbols/008-greek-and-coptic.lyx

@@ -1,5 +1,5 @@
-#LyX 2.3 created this file. For more info see http://www.lyx.org/
-\lyxformat 515
+#LyX 2.4 created this file. For more info see https://www.lyx.org/
+\lyxformat 566
 \begin_document
 \begin_header
 \save_transient_properties true
@@ -14,7 +14,7 @@
 \language english
 \language_package default
 \inputencoding utf8
-\fontencoding global
+\fontencoding auto
 \font_roman "lmodern" "default"
 \font_sans "lmss" "default"
 \font_typewriter "lmtt" "default"
@@ -26,6 +26,7 @@
 \font_sf_scale 100 100
 \font_tt_scale 100 100
 \use_microtype false
+\use_dash_ligatures true
 \graphics default
 \default_output_format pdf2
 \output_sync 0
@@ -55,6 +56,7 @@
 \suppress_date false
 \justification true
 \use_refstyle 0
+\use_minted 0
 \index Index
 \shortcut idx
 \color #008000
@@ -63,7 +65,10 @@
 \tocdepth 3
 \paragraph_separation skip
 \defskip medskip
-\quotes_language english
+\is_math_indent 0
+\math_numbering_side default
+\quotes_style english
+\dynamic_quotes 0
 \papercolumns 1
 \papersides 1
 \paperpagestyle default
@@ -92,6 +97,7 @@ textalpha
 LatexCommand href
 name "#9681"
 target "http://www.lyx.org/trac/ticket/9681"
+literal "false"
 
 \end_inset
 
@@ -281,7 +287,7 @@ Greek in math (only characters supported by TeX in math-mode)
 \begin_layout Labeling
 \labelwidthstring 00.00.0000
 950 
-\begin_inset Formula $ζηθικλμνξο$
+\begin_inset Formula $ζηθικλμνξ$
 \end_inset
 
 
@@ -316,7 +322,7 @@ Greek in math (only characters supported by TeX in math-mode)
 
 \begin_layout Labeling
 \labelwidthstring 00.00.0000
-990 
+990
 \end_layout
 
 \begin_layout Labeling