Revise some comments and strings

These are a few things I had missed in gitpython-developers#1725.

Author: EliahKagan

Diff for: git/config.py

@@ -150,6 +150,7 @@ class SectionConstraint(Generic[T_ConfigParser]):
     """
 
     __slots__ = ("_config", "_section_name")
+
     _valid_attrs_ = (
         "get_value",
         "set_value",

Diff for: git/objects/base.py

@@ -137,7 +137,7 @@ def __repr__(self) -> str:
     @property
     def hexsha(self) -> str:
         """:return: 40 byte hex version of our 20 byte binary sha"""
-        # b2a_hex produces bytes
+        # b2a_hex produces bytes.
         return bin_to_hex(self.binsha).decode("ascii")
 
     @property
@@ -206,7 +206,7 @@ def __hash__(self) -> int:
 
     def _set_cache_(self, attr: str) -> None:
         if attr in IndexObject.__slots__:
-            # they cannot be retrieved lateron ( not without searching for them )
+            # They cannot be retrieved later on (not without searching for them).
             raise AttributeError(
                 "Attribute '%s' unset: path and mode attributes must have been set during %s object creation"
                 % (attr, type(self).__name__)

Diff for: git/refs/symbolic.py

@@ -215,7 +215,7 @@ def _check_ref_name_valid(ref_path: PathLike) -> None:
         elif any(component.endswith(".lock") for component in str(ref_path).split("/")):
             raise ValueError(
                 f"Invalid reference '{ref_path}': references cannot have slash-separated components that end with"
-                f" '.lock'"
+                " '.lock'"
             )
 
     @classmethod
@@ -309,8 +309,8 @@ def set_commit(
     ) -> "SymbolicReference":
         """As set_object, but restricts the type of object to be a Commit.
 
-        :raise ValueError: If commit is not a Commit object or doesn't point to
-            a commit
+        :raise ValueError: If commit is not a :class:`~git.objects.commit.Commit` object
+            or doesn't point to a commit
         :return: self
         """
         # Check the type - assume the best if it is a base-string.