Add 7.5.0 to _buttons.html

For some reason this didn't happen in baa9e55. Also took this chance to delete some really old versions.

PiperOrigin-RevId: 722759259
Change-Id: Ia117670142dab2406ba839a951d15218cb287b33

site/en/_buttons.html

@@ -28,6 +28,12 @@
 <a href="/versions/8.0.0{% dynamic print setvar.original_path %}">8.0</a>
 {% dynamic endif %}
 ·
+{% dynamic if setvar.version == "7.5.0" %}
+<strong>7.5</strong>
+{% dynamic else %}
+<a href="/versions/7.5.0{% dynamic print setvar.original_path %}">7.5</a>
+{% dynamic endif %}
+·
 {% dynamic if setvar.version == "7.4.0" %}
 <strong>7.4</strong>
 {% dynamic else %}
@@ -45,24 +51,6 @@
 {% dynamic else %}
 <a href="/versions/7.2.0{% dynamic print setvar.original_path %}">7.2</a>
 {% dynamic endif %}
-·
-{% dynamic if setvar.version == "7.1.0" %}
-<strong>7.1</strong>
-{% dynamic else %}
-<a href="/versions/7.1.0{% dynamic print setvar.original_path %}">7.1</a>
-{% dynamic endif %}
-·
-{% dynamic if setvar.version == "7.0.0" %}
-<strong>7.0</strong>
-{% dynamic else %}
-<a href="/versions/7.0.0{% dynamic print setvar.original_path %}">7.0</a>
-{% dynamic endif %}
-·
-{% dynamic if setvar.version == "6.5.0" %}
-<strong>6.5</strong>
-{% dynamic else %}
-<a href="/versions/6.5.0{% dynamic print setvar.original_path %}">6.5</a>
-{% dynamic endif %}
 <!-- END_VERSION_INDICATOR -->
 </span>
 <p/>