gh-36464: fix doctest in `src/sage/combinat/posets/posets.py`
    
The following doctest in `sage/combinat/posets/posets.py" is failing on
some systems, e.g., here on fedora 35.

```py
sage -t --long --warn-long 14.4 --random-
seed=28988349073943040517554297060681045316
src/sage/combinat/posets/posets.py
**********************************************************************
File "src/sage/combinat/posets/posets.py", line 1374, in
sage.combinat.posets.posets.FinitePoset._latex_
Failed example:
    print(P._latex_())  # optional - dot2tex graphviz
Expected:
    \begin{tikzpicture}[>=latex,line join=bevel,]
    %%
    \node (node_...) at (5...bp,...bp) [draw,draw=none] {$...$};
      \node (node_...) at (5...bp,...bp) [draw,draw=none] {$...$};
      \draw [black,->] (node_...) ..controls (...bp,...bp) and
(...bp,...bp)  .. (node_...);
    %
    \end{tikzpicture}
Got:
    \begin{tikzpicture}[>=latex,line join=bevel,]
    %%
    \node (node_0) at (6.0bp,6.5bp) [draw,draw=none] {$1$};
      \node (node_1) at (6.0bp,55.5bp) [draw,draw=none] {$2$};
      \draw [black,->] (node_0) ..controls (6.0bp,19.603bp) and
(6.0bp,30.062bp)  .. (node_1);
    %
    \end{tikzpicture}
```
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URL: #36464
Reported by: David Coudert
Reviewer(s): Kwankyu Lee

Author: Release Manager

src/sage/combinat/posets/posets.py

@@ -1372,8 +1372,8 @@ def _latex_(self):
             sage: print(P._latex_())  # optional - dot2tex graphviz
             \begin{tikzpicture}[>=latex,line join=bevel,]
             %%
-            \node (node_...) at (5...bp,...bp) [draw,draw=none] {$...$};
-              \node (node_...) at (5...bp,...bp) [draw,draw=none] {$...$};
+            \node (node_...) at (...bp,...bp) [draw,draw=none] {$...$};
+              \node (node_...) at (...bp,...bp) [draw,draw=none] {$...$};
               \draw [black,->] (node_...) ..controls (...bp,...bp) and (...bp,...bp)  .. (node_...);
             %
             \end{tikzpicture}