Replace ^ with & in three tests

This prevents build system found in build `4077` from failing tests erroneously

Author: axemonk

tests/syntax_test_excel.xls.txt

@@ -681,7 +681,7 @@ TEXTJOIN(";",FALSE,valmax)
 '     ^^ meta.reference.cell.sheet storage.type.sheet
 ' <- keyword.operator.assignment.sheet
 
-='^'!A1
+='&'!A1
 '^^^^ meta.reference.sheet
 '^ punctuation.definition.annotation.begin.sheet
 ' ^ entity.name.struct.sheet

tests/syntax_test_google.gsheet.txt

@@ -702,7 +702,7 @@ TEXTJOIN(";",FALSE,valmax)
 '    ^ punctuation.separator.sequence.sheet
 '     ^^ meta.reference.cell.sheet storage.type.sheet
 
-='^'!A1
+='&'!A1
 '^^^^ meta.reference.sheet
 '^ punctuation.definition.annotation.begin.sheet
 ' ^ entity.name.struct.sheet

tests/syntax_test_libre_references.localc.txt

@@ -90,7 +90,7 @@
 '     ^^ meta.reference.cell.sheet storage.type.sheet
 ' <- keyword.operator.assignment.sheet
 
-='^'!A1
+='&'!A1
 '^^^^^^ meta.reference - meta.reference meta.reference
 '^^^^ meta.reference.sheet
 '^ punctuation.definition.annotation.begin.libre