docs: Fix hotdoc warnings [skip ci]

Hotdoc really wants internal links to point to the .md files instead of
the generated names. Which makes sense, as we're currently relying on
the fact that meson only generated .html pages.

docs/markdown/Python-3-module.md

@@ -3,17 +3,17 @@
 This module provides support for dealing with Python 3. It has the
 following methods.
 
-This module is deprecated and replaced by the [python](Python-module.html) module.
+This module is deprecated and replaced by the [python](Python-module.md) module.
 
 ## find_python
 
 This is a cross platform way of finding the Python 3 executable, which
 may have a different name on different operating systems. Returns an
-[external program](Reference-manual.html#external-program-object) object.
+[external program](Reference-manual.md#external-program-object) object.
 
 *Added 0.38.0*
 
-Deprecated, replaced by [`find_installation`](Python-module.html#find_installation)
+Deprecated, replaced by [`find_installation`](Python-module.md#find_installation)
 function from `python` module.
 
 ## extension_module
@@ -29,7 +29,7 @@ need to add `dependencies : dependency('python3')`, see
 
 *Added 0.38.0*
 
-Deprecated, replaced by [`extension_module`](Python-module.html#extension_module)
+Deprecated, replaced by [`extension_module`](Python-module.md#extension_module)
 method from `python` module.
 
 ## language_version
@@ -38,7 +38,7 @@ Returns a string with the Python language version such as `3.5`.
 
 *Added 0.40.0*
 
-Deprecated, replaced by [`language_version`](Python-module.html#language_version)
+Deprecated, replaced by [`language_version`](Python-module.md#language_version)
 method from `python` module.
 
 ## sysconfig_path
@@ -48,5 +48,5 @@ Returns the Python sysconfig path without prefix, such as
 
 *Added 0.40.0*
 
-Deprecated, replaced by [`get_path`](Python-module.html#get_path)
+Deprecated, replaced by [`get_path`](Python-module.md#get_path)
 method from `python` module.

docs/markdown/Reference-manual.md

@@ -1555,7 +1555,7 @@ the following methods.
   compilation to reduce build time) and `false` otherwise.
 
 - `override_find_program(progname, program)` [*(Added
-  0.46.0)*](Release-notes-for-0-46-0.html#can-override-find_program)
+  0.46.0)*](Release-notes-for-0.46.0.md#can-override-find_program)
   specifies that whenever `find_program` is used to find a program
   named `progname`, Meson should not not look it up on the system but
   instead return `program`, which may either be the result of
@@ -1589,7 +1589,7 @@ methods:
   etc.
 
 - `system()` returns the operating system name.  [This
-  table](Reference-tables.html#operating-system-names) Lists all of
+  table](Reference-tables.md#operating-system-names) Lists all of
   the currently known Operating System names, these are guaranteed to
   continue working.
 
@@ -1691,7 +1691,7 @@ the following methods:
   the compiler would. E.g. `"a" "b"` will become `"ab"`.
 
 - `get_id()` returns a string identifying the compiler. For example,
-  `gcc`, `msvc`, [and more](Reference-tables.html#compiler-ids).
+  `gcc`, `msvc`, [and more](Reference-tables.md#compiler-ids).
 
 - `get_supported_arguments(list_of_string)` *(added 0.43.0)* returns
   an array containing only the arguments supported by the compiler,
@@ -1790,7 +1790,7 @@ the following methods:
   compiler supports the GNU style (`__attribute__(...)`) `name`. This is
   preferable to manual compile checks as it may be optimized for compilers that
   do not support such attributes.
-  [This table](Reference-tables.html#gcc-attribute-support) Lists all of the
+  [This table](Reference-tables.md#gcc-attribute-support) Lists all of the
   supported attributes.
 
 - `get_supported_function_attributes(list_of_names)` *(added in 0.48.0)