docs: fixed some build errors

docs/admin/sec-sophos-umc.rst

@@ -1,4 +1,4 b''
-.. _sec-your-server:
+.. _sec-sophos-umc:
 
 Securing Your Server via Sophos UTM 9
 -------------------------------------

docs/conf.py

@@ -34,7 +34,7 b' import common'
 extensions = [
     'sphinx.ext.intersphinx',
     'sphinx.ext.todo',
-    'sphinx.ext.pngmath'
+    'sphinx.ext.imgmath'
 ]
 
 intersphinx_mapping = {

docs/tutorials/deploy-from-host.rst

@@ -88,7 +88,7 b' 2. Once downloaded to your computer, tra'
 
 The |RCC| installer is now on your server, and you can read the full
 instructions here
-:ref:`Install RhodeCode Control <control:rcc-install-ref>`,
+:ref:`Install RhodeCode Control <control:rcc-linux-ref>` ,
 but below is the example shortcut.
 
 .. code-block:: bash