Add note suggesting dropping try on non error-unions

[mikastiv]

Resolves #21845

Output on test/cases/compile_errors/comptime_try_non_error.zig:

test/cases/compile_errors/comptime_try_non_error.zig:6:12: error: expected error union type, found 'u8'
    try bar();
        ~~~^~
test/cases/compile_errors/comptime_try_non_error.zig:6:12: note: consider omitting 'try'
test/cases/compile_errors/comptime_try_non_error.zig:2:8: note: called from here
    foo();
    ~~~^~

Output on example from issue:

> stage4/bin/zig build-exe a.zig
a.zig:6:44: error: expected error union type, found 'array_list.ArrayListAligned(u8,null)'
    const list = try std.ArrayList(u8).init(std.heap.page_allocator);
                     ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
a.zig:6:44: note: consider omitting 'try'

[mlugg]

Sorry for the delay in review. I'll rebase this and set to auto-merge shortly.