chore(topology/instances/real): remove instance real_maps_algebra (#…

…6920)

Remove 
```lean
instance reals_semimodule : has_continuous_smul ℝ ℝ
instance real_maps_algebra {α : Type*} [topological_space α] : algebra ℝ C(α, ℝ)
```
These are not used explicitly anywhere in the library, I suspect because if needed they can be found by typeclass inference.  Deleting them cleans up the import hierarchy by requiring many fewer files to import `topology.continuous_function.algebra`.

src/measure_theory/ae_eq_fun.lean

@@ -5,6 +5,7 @@ Authors: Johannes Hölzl, Zhouhang Zhou
 -/
 import measure_theory.integration
 import order.filter.germ
+import topology.continuous_function.algebra
 
 /-!
 

src/topology/continuous_function/bounded.lean

@@ -4,6 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Sébastien Gouëzel, Mario Carneiro, Yury Kudryashov, Heather Macbeth
 -/
 import analysis.normed_space.basic
+import topology.continuous_function.algebra
 
 /-!
 # Bounded continuous functions

src/topology/instances/real.lean

@@ -6,7 +6,6 @@ Authors: Johannes Hölzl, Mario Carneiro
 import topology.metric_space.basic
 import topology.algebra.uniform_group
 import topology.algebra.ring
-import topology.continuous_function.algebra
 import ring_theory.subring
 import group_theory.archimedean
 /-!
@@ -285,11 +284,6 @@ eq_Icc_of_connected_compact ⟨(nonempty_Icc.2 hab).image f, is_preconnected_Icc
 
 end
 
-instance reals_semimodule : has_continuous_smul ℝ ℝ := ⟨continuous_mul⟩
-
-instance real_maps_algebra {α : Type*} [topological_space α] :
-  algebra ℝ C(α, ℝ) := continuous_map_algebra
-
 section subgroups
 
 /-- Given a nontrivial subgroup `G ⊆ ℝ`, if `G ∩ ℝ_{>0}` has no minimum then `G` is dense. -/