Mark some mjData fields as mutable.

PiperOrigin-RevId: 815819490
Change-Id: I1a62fda556b4197aec451f2747c69f34bab13220

python/mujoco/introspect/structs.py

@@ -5003,12 +5003,12 @@ STRUCTS: Mapping[str, StructDecl] = dict([
              StructFieldDecl(
                  name='pstack',
                  type=ValueType(name='size_t'),
-                 doc='first available byte in stack',
+                 doc='first available byte in stack (mutable)',
              ),
              StructFieldDecl(
                  name='pbase',
                  type=ValueType(name='size_t'),
-                 doc='value of pstack when mj_markStack was last called',
+                 doc='value of pstack when mj_markStack was last called (mutable)',  # pylint: disable=line-too-long
              ),
              StructFieldDecl(
                  name='parena',
@@ -5018,7 +5018,7 @@ STRUCTS: Mapping[str, StructDecl] = dict([
              StructFieldDecl(
                  name='maxuse_stack',
                  type=ValueType(name='mjtSize'),
-                 doc='maximum stack allocation in bytes',
+                 doc='maximum stack allocation in bytes (mutable)',
              ),
              StructFieldDecl(
                  name='maxuse_threadstack',
@@ -5081,7 +5081,7 @@ STRUCTS: Mapping[str, StructDecl] = dict([
                      inner_type=ValueType(name='mjWarningStat'),
                      extents=(8,),
                  ),
-                 doc='warning statistics',
+                 doc='warning statistics (mutable)',
              ),
              StructFieldDecl(
                  name='timer',