You should be able to get what you want by removing this statement:
ods excel options(sheet_name="sheet2" sheet_interval="proc");
In fact, you can reduce it a bit more. When I run the following, I get one sheet, with output from both procs:
ods excel file ="c:\temp\Tuesday.xlsx" style=HTMLblue options(sheet_interval="none" sheet_name="Sheet1");
ods escapechar='~';
ods text="~S={font_size=14pt font_weight=bold}~This is the first bit of output";
proc print data=sashelp.cars(obs=10);
run;
ods text="~S={font_size=14pt font_weight=bold}~This is the second bit of output";
ods excel options(sheet_name="sheet2" sheet_interval="none");
proc print data=sashelp.class;
run;
ods excel close;
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